The SQLite tokeniser does not deal with scripts that do not use spaces
for word breaking (CJK, Thai, etc), thus searching in those languages
does not work well.
This adds a custom SQLite tokeniser based on ICU that breaks words for
all languages supported by that library, and uses NFKC_Casefold
normalisation to handle normalisation, case folding, and dropping of
ignorable characters.
Fixes#121
7e38198287