Implement char/short/int_fetch_and_add for msftc/x86[_64] (Win32)

Implement char/short/int_fetch_and_add for msftc/x86[_64] (Win32)

* src/atomic_ops/sysdeps/msftc/x86.h (AO_NO_ASM_XADD): Recognize new
macro.
* src/atomic_ops/sysdeps/msftc/x86.h (AO_char_fetch_and_add_full,
AO_short_fetch_and_add_full): New primitive implemented using __asm
(only unless AO_NO_ASM_XADD).
* src/atomic_ops/sysdeps/msftc/x86.h (AO_HAVE_char_fetch_and_add_full,
AO_HAVE_short_fetch_and_add_full): New macro (accompanying the
corresponding primitive).
* src/atomic_ops/sysdeps/msftc/x86_64.h
(AO_HAVE_int_fetch_and_add_full, AO_HAVE_char_fetch_and_add_full,
AO_HAVE_short_fetch_and_add_full): Likewise.
* src/atomic_ops/sysdeps/msftc/x86_64.h (_InterlockedExchangeAdd): Add
pragma to specify the intrinsic.
* src/atomic_ops/sysdeps/msftc/x86_64.h (AO_int_fetch_and_add_full):
New primitive (implemented using 32-bit InterlockedExchangeAdd).
* src/atomic_ops/sysdeps/msftc/x86_64.h  (AO_char_fetch_and_add_full,
AO_short_fetch_and_add_full): New primitive implemented using 64-bit
__asm (only if AO_ASM_X64_AVAILABLE).