C11 cleanups
We now depend on C11, but we never really cleaned out our C99 or C11 compatibility shims while bumping this.
This cleans those out, leaving only a few:
-
c99_compat.h
is still around, for the sole reason of supporting therestrict
-keyword from C++ code. -
c11/threads.h
is still around, because blargh, C11 threads is optional, and MSVC doesn't support it.
In addition, this cleans up a tiny bit of Windows specific meson build-glue.