[9] Locale for MSVCRT

- Use the CRT __pctype_func to retrieve ctype
- Set the locale masks to the correct values for the CRT
- Make initialization of locale::id and once_flag trivial. MSVC does not implement constexpr yet, so their global initialization is not static, and it results in initialization order issues otherwise (the locale ids are initializated lazily too early, dynamic initialization later zeroes them)
[1] Link with c++.lib now that it builds