Fixes Bugzilla #2895.
His notes:
The following trivial changes make SDL2 tree (mostly) compatible with Visual
Studio 2005:
* SDL_stdlib.c: Similar to VS2010 and newer, VS2005 also generates memcpy(),
(it also generates memset(), see below), so propagate the #if condition to
cover VS2005.
* SDL_pixels.c (SDL_CalculateGammaRamp): VS2005 generates a memset() call for
gamma==0 case, so replace the if loop with SDL_memset().
* SDL_windowsvideo.h: Include msctf.h only with VS2008 and newer, otherwise
include SDL_msctf.h
* SDL_windowskeyboard.c: Adjust the #ifdefs so that SDL_msctf.h inclusion is
always recognized correctly.