SADXModLoader.rc: Added a resource script.

The resource script contains a VS_VERSION_INFO resource.
There's also an auto-generated manifest added by MSVC 2010.

config.SADXModLoader.h.in: Changed version prefixes to MODLOADER_*.
dllmain.cpp: Use MODLOADER_*, not SADXMODLOADER_*.
cmake/platform/msvc.cmake: Explicitly set -subsystem:5.01

MSVC 2010 doesn't work on anything older than XP SP2 (officially).

MSVC 2013 does support XP, but only if the subsystem is explicitly
set to 5.01.