Various source cleanups, especially ushMEOW.cpp and fiopen.cpp

[Stephan T. Lavavej (StephanTLavavej)]

This is structured as a series of commits for easier reviewing.

• stl/src is always built with real wchar_t, so we don't need to test #ifdef _NATIVE_WCHAR_T_DEFINED.
• ushMEOW.cpp cleanups:
  • Only the ushMEOW.cpp files #define wistream, so we don't need to test #ifndef wistream.
  • Each ushMEOW.cpp only needs to macroize its corresponding _Init_wMEOW and init_wMEOW.
  • Consistency: ushMEOW.cpp should #define _Winit last (as ushcerr.cpp already did).
  • Each wMEOW.cpp already includes , so ushMEOW.cpp doesn't need to do so explicitly.
  • Fix copy-pasted comments in ushMEOW.cpp (only ushcerr.cpp was correct).
• fiopen.cpp cleanups:
  • fiopen.cpp doesn't need to include at all.
  • Move fiopen.cpp helpers into an unnamed namespace.
    • Ignore whitespace when viewing this commit.
    • Precedent for the using-declaration:

      STL/stl/src/syserror.cpp

      Lines 17 to 18 in ea32e86

      	namespace {
      	using _STD errc;

    • These helpers were neither dllexported nor mentioned by stl/inc, so they're safe to move into an unnamed namespace. (This makes it clear that they're internal helpers that aren't needed by other source files, and slightly helps static linking by avoiding symbols with external linkage that no user code will ever need to look for.)

[Stephan T. Lavavej (StephanTLavavej)]

I'm mirroring this to the MSVC-internal repo - please notify me if any further changes are pushed.