Update some API docs for Nonblocking.Lock and subclasses.

src/engine/nonblocking/nonblocking-lock.vala

@@ -16,7 +16,8 @@
  * pass. Another asynchronous task may call {@link notify} to mark the
  * lock as being safe, notifying waiting tasks. Once marked as being
  * safe to pass, a lock may be reset to being unsafe by calling {@link
- * reset}.
+ * reset}. The lock cannot be passed initially, if this is desired
+ * call notify after constructing it.
  *
  * See the specialised sub-classes for concrete implementations,
  * which vary based on two features:
@@ -84,6 +85,9 @@ public abstract class Geary.Nonblocking.Lock : BaseObject {
     private bool passed = false;
     private Gee.List<Pending> pending_queue = new Gee.LinkedList<Pending>();
 
+    /**
+     * Constructs a new lock that is initially not able to be passed.
+     */
     protected Lock(bool broadcast, bool autoreset, Cancellable? cancellable = null) {
         this.broadcast = broadcast;
         this.autoreset = autoreset;

src/engine/nonblocking/nonblocking-variants.vala

@@ -19,9 +19,16 @@
  * @see Lock
  */
 public class Geary.Nonblocking.Semaphore : Geary.Nonblocking.Lock {
+
+    /**
+     * Constructs a new semaphore lock.
+     *
+     * The new lock is initially not able to be passed.
+     */
     public Semaphore(Cancellable? cancellable = null) {
         base (true, false, cancellable);
     }
+
 }
 
 /**
@@ -37,9 +44,16 @@ public class Geary.Nonblocking.Semaphore : Geary.Nonblocking.Lock {
  * @see Lock
  */
 public class Geary.Nonblocking.Event : Geary.Nonblocking.Lock {
+
+    /**
+     * Constructs a new event lock.
+     *
+     * The new lock is initially not able to be passed.
+     */
     public Event(Cancellable? cancellable = null) {
         base (true, true, cancellable);
     }
+
 }
 
 /**
@@ -55,7 +69,14 @@ public class Geary.Nonblocking.Event : Geary.Nonblocking.Lock {
  * @see Lock
  */
 public class Geary.Nonblocking.Spinlock : Geary.Nonblocking.Lock {
+
+    /**
+     * Constructs a new spin lock.
+     *
+     * The new lock is initially not able to be passed.
+     */
     public Spinlock(Cancellable? cancellable = null) {
         base (false, true, cancellable);
     }
+
 }