nedmalloc: allow compiling with MSys2's compiler
nedmalloc: allow compiling with MSys2's compiler

With MSys2's GCC, `ReadWriteBarrier` is already defined, and FORCEINLINE
unfortunately gets defined incorrectly.

Let's work around both problems, using the MSys2-specific
__MINGW64_VERSION_MAJOR constant to guard the FORCEINLINE definition so
as not to affect other platforms.

Signed-off-by: Johannes Schindelin <53fb8db7833fca1e1746dd8592f61048d350f64c@gmx.de>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git