libmonoutils: Removed need for X64 MASM definition
Check for availability of the RAX register, checking if we're running x64
Moved _WIN32_WINNT to winconfig.h; dropped support for WinXP SP1 and below
Win32 compilation was broken due to attempting to use Interlocked* functions introduced with XP SP2.
Added file-mmap-windows.c to libmonoruntime.vcxproj
libmono.vcxproj: Link to libmonoruntimesgen.lib in the Release_SGen mode
Previously attempted to link to the libmonoruntime library outputted by the boehm configuration