Problem: Add an object, name it using cyrilic, Slice, click Export: the proposed name is mangled. Affects all platforms, 2.2.0 was fine.
Cause: It is mangled during ASCII folding, which was broken with 28c0880 when it was generalized to be used from the fuzzy matcher.
fold_to_ascii(wchar_t c, char *out) relies on narrowing char = wchar_t assignment, the old one used std::back_insert_iterator<std::wstring>.
It is thus unable to leave a character alone even when it should (it should, right?).
Solution:
1. Typed the fold_to_ascii function so it works on wchar_t only, which should mimic the old behaviour.
2. Changed the respective call in fts_fuzzy_match.h. That function also works with wide char C-strings.
Cleanup:
1. Removed the unused fold_utf8_to_ascii(const char *src) overload to avoid code duplication.
2. Untemplated the fold_to_ascii(wchar_t c, std::back_insert_iterator<std::wstring>& out) function, it was never called with a different type.
3. The function is now static in ASCIIFolding.cpp, nobody else needs to know.
