64-bit volatile accesses are not atomic on i386. Both i686-w64-mingw32-gcc and x86 MSVC splits 64-bit loads into a pair of load/store ops.
Fix this by using a FILD/FISTP pair, which is also used to implement C11 atomics by i686-w64-mingw32-gcc.
Fixes: f82b1c1fcf770a5d6fa02c3f286282be79a201b8
-- v4: include: Prevent misuse of __WINE_ATOMIC_* helper macros for non-atomic large accesses. include: Fix ReadNoFence64 on i386.