Remove mingw-w64 version of _fmode. _fmode should not be linked directly into the executable. Instead, the export from msvcrt should be used. On Windows 10 it's defined to *__p__fmode(), which is exported from ucrtbase.dll
Also _fmode in msvcrt.dll is initialized with 0.
We previously used 2 different versions: one from wine and one from mingw-w64.
The former was used in msvcrt, the latter was statically compiled into the executable. When using MS libs, there is only one _matherr, which is statically linked into the executable and does nothing (it's not really a function for users to be called).
_setusermatherror should only exist in msvcrt and not statically, which wouldn't work at all.