Remove a number of redundant fns in Engine.Util.Ascii.

* src/engine/util/util-ascii.vala (Geary.Ascii): Remove functions that
  are now supported by Vala 0.26, that are simple statements, or are only
  used once elsewhere. Update call sites.

src/engine/imap/message/imap-data-format.vala

@@ -25,7 +25,7 @@ private bool is_special_char(char ch, char[] ar, string? exceptions) {
         return true;
 
     if (ch in ar)
-        return (exceptions != null) ? Ascii.index_of(exceptions, ch) < 0 : true;
+        return (exceptions != null) ? exceptions.index_of_char(ch) < 0 : true;
 
     return false;
 }

src/engine/imap/message/imap-fetch-body-data-specifier.vala

@@ -78,7 +78,7 @@ public class Geary.Imap.FetchBodyDataSpecifier : BaseObject, Gee.Hashable<FetchB
             if (String.is_empty(value))
                 return NONE;
 
-            switch (Ascii.strdown(value)) {
+            switch (value.down()) {
                 case "header":
                     return HEADER;
 
@@ -180,9 +180,11 @@ public class Geary.Imap.FetchBodyDataSpecifier : BaseObject, Gee.Hashable<FetchB
         this.is_peek = is_peek;
 
         if (field_names != null && field_names.length > 0) {
-            this.field_names = new Gee.TreeSet<string>(Ascii.strcmp);
+            this.field_names = new Gee.TreeSet<string>((s1, s2) => {
+                    return GLib.strcmp(s1, s2);
+                });
             foreach (string field_name in field_names) {
-                string converted = Ascii.strdown(field_name.strip());
+                string converted = field_name.strip().down();
 
                 if (!String.is_empty(converted))
                     this.field_names.add(converted);

src/engine/imap/message/imap-internal-date.vala

@@ -70,7 +70,7 @@ public class Geary.Imap.InternalDate : Geary.MessageData.AbstractMessageData, Ge
 
         // check month (this catches localization problems)
         int month = -1;
-        string mon_down = Ascii.strdown(((string) mon));
+        string mon_down = ((string) mon).down();
         for (int ctr = 0; ctr < EN_US_MON_DOWN.length; ctr++) {
             if (mon_down == EN_US_MON_DOWN[ctr]) {
                 month = ctr;

src/engine/imap/message/imap-mailbox-specifier.vala

@@ -85,7 +85,7 @@ public class Geary.Imap.MailboxSpecifier : BaseObject, Gee.Hashable<MailboxSpeci
      * @see is_inbox_name
      */
     public static bool is_canonical_inbox_name(string name) {
-        return Ascii.str_equal(name, CANONICAL_INBOX_NAME);
+        return (name == CANONICAL_INBOX_NAME);
     }
 
     /**
@@ -183,7 +183,7 @@ public class Geary.Imap.MailboxSpecifier : BaseObject, Gee.Hashable<MailboxSpeci
         if (is_inbox)
             return Ascii.stri_equal(name, other.name);
 
-        return Ascii.str_equal(name, other.name);
+        return (name == other.name);
     }
 
     public int compare_to(MailboxSpecifier other) {
@@ -193,7 +193,7 @@ public class Geary.Imap.MailboxSpecifier : BaseObject, Gee.Hashable<MailboxSpeci
         if (is_inbox && other.is_inbox)
             return 0;
 
-        return Ascii.strcmp(name, other.name);
+        return GLib.strcmp(name, other.name);
     }
 
     public string to_string() {

src/engine/imap/parameter/imap-string-parameter.vala

@@ -139,7 +139,7 @@ public abstract class Geary.Imap.StringParameter : Geary.Imap.Parameter {
      * Case-sensitive comparison.
      */
     public bool equals_cs(string value) {
-        return Ascii.str_equal(ascii, value);
+        return (ascii == value);
     }
 
     /**
@@ -153,14 +153,14 @@ public abstract class Geary.Imap.StringParameter : Geary.Imap.Parameter {
      * Returns the string lowercased.
      */
     public string as_lower() {
-        return Ascii.strdown(ascii);
+        return ascii.down();
     }
 
     /**
      * Returns the string uppercased.
      */
     public string as_upper() {
-        return Ascii.strup(ascii);
+        return ascii.up();
     }
 
     /**

src/engine/imap/response/imap-response-code-type.vala

@@ -72,7 +72,7 @@ public class Geary.Imap.ResponseCodeType : BaseObject, Gee.Hashable<ResponseCode
 
         // store lowercased so it's easily compared with const strings above
         original = ascii;
-        value = Ascii.strdown(ascii);
+        value = ascii.down();
     }
 
     public bool is_value(string str) {

src/engine/mime/mime-content-parameters.vala

@@ -87,7 +87,7 @@ public class Geary.Mime.ContentParameters : BaseObject {
     public bool has_value_cs(string attribute, string value) {
         string? stored = params.get(attribute);
 
-        return (stored != null) ? Ascii.str_equal(stored, value) : false;
+        return (stored != null) ? (stored == value) : false;
     }
 
     /**

src/engine/mime/mime-disposition-type.vala

@@ -35,7 +35,7 @@ public enum Geary.Mime.DispositionType {
         if (String.is_empty_or_whitespace(str))
             return UNSPECIFIED;
 
-        switch (Ascii.strdown(str)) {
+        switch (str.down()) {
             case "inline":
                 return INLINE;
 

src/engine/mime/mime-multipart-subtype.vala

@@ -53,7 +53,7 @@ public enum Geary.Mime.MultipartSubtype {
         }
 
         is_unknown = false;
-        switch (Ascii.strdown(content_type.media_subtype)) {
+        switch (content_type.media_subtype.down()) {
             case "mixed":
                 return MIXED;
 

src/engine/rfc822/rfc822-mailbox-address.vala

@@ -53,7 +53,7 @@ public class Geary.RFC822.MailboxAddress : Geary.MessageData.SearchableMessageDa
 
         source_route = null;
 
-        int atsign = Ascii.index_of(address, '@');
+        int atsign = address.index_of_char('@');
         if (atsign > 0) {
             mailbox = address.slice(0, atsign);
             domain = address.slice(atsign + 1, address.length);

src/engine/smtp/smtp-command.vala

@@ -58,7 +58,7 @@ public enum Geary.Smtp.Command {
     }
 
     public static Command deserialize(string str) throws SmtpError {
-        switch (Ascii.strdown(str)) {
+        switch (str.down()) {
             case "helo":
                 return HELO;
 

src/engine/smtp/smtp-greeting.vala

@@ -27,7 +27,7 @@ public class Geary.Smtp.Greeting : Response {
         }
 
         public static ServerFlavor deserialize(string str) {
-            switch (Ascii.strup(str)) {
+            switch (str.up()) {
                 case "SMTP":
                     return SMTP;
 

src/engine/util/util-ascii.vala

@@ -4,63 +4,32 @@
  * (version 2.1 or later).  See the COPYING file in this distribution.
  */
 
-// These calls are bound to the string class in Vala 0.26.  When that version of Vala is the
-// minimum, these can be dropped and Ascii.strup and Ascii.strdown can use the string methods.
-extern string g_ascii_strup(string str, ssize_t len = -1);
-extern string g_ascii_strdown(string str, ssize_t len = -1);
-
 namespace Geary.Ascii {
 
-public int index_of(string str, char ch) {
-    char *strptr = str;
-    int index = 0;
-    for (;;) {
-        char strch = *strptr++;
-        
-        if (strch == String.EOS)
-            return -1;
-        
-        if (strch == ch)
-            return index;
-        
-        index++;
-    }
-}
-
 public bool get_next_char(string str, ref int index, out char ch) {
     ch = str[index++];
 
     return ch != String.EOS;
 }
 
-public inline int strcmp(string a, string b) {
-    return GLib.strcmp(a, b);
-}
-
-public int stricmp(string a, string b) {
+public bool stri_equal(string a, string b) {
+    // XXX Is this marginally faster than a.down() == b.down() in the
+    // best case, slower in the worse case, so not worth it?
     char *aptr = a;
     char *bptr = b;
     for (;;) {
         int diff = (int) (*aptr).tolower() - (int) (*bptr).tolower();
         if (diff != 0)
-            return diff;
+            return false;
 
         if (*aptr == String.EOS)
-            return 0;
+            return true;
 
         aptr++;
         bptr++;
     }
 }
 
-public inline bool str_equal(string a, string b) {
-    return a == b;
-}
-
-public inline bool stri_equal(string a, string b) {
-    return stricmp(a, b) == 0;
-}
-
 public bool nullable_stri_equal(string? a, string? b) {
     if (a == null)
         return (b == null);
@@ -86,14 +55,6 @@ public uint nullable_stri_hash(string? str) {
     return (str != null) ? stri_hash(str) : 0;
 }
 
-public string strdown(string str) {
-    return g_ascii_strdown(str);
-}
-
-public string strup(string str) {
-    return g_ascii_strup(str);
-}
-
 /**
  * Returns true if the ASCII string contains only whitespace and at least one numeric character.
  */