Beginning of the upstreaming process of Git for Windows effort.
* js/msys2:
mingw: uglify (a, 0) definitions to shut up warnings
mingw: squash another warning about a cast
mingw: avoid warnings when casting HANDLEs to int
mingw: avoid redefining S_* constants
compat/winansi: support compiling with MSys2
compat/mingw: support MSys2-based MinGW build
nedmalloc: allow compiling with MSys2's compiler
config.mak.uname: supporting 64-bit MSys2
config.mak.uname: support MSys2