I was lazy and just renamed SDL_win32_main's stdout.txt - but I still
added the dhewm3log-old.txt backup function.
I also renamed Sys_GetHomeDir() to Win_GetHomeDir() as it's Win32-only
On Windows it's in Documents\My Games\dhewm3\dhewm3log.txt
Don't link against SDLmain.[a|lib], always compile it.
We can use pure C MinGW cross compiled libraries with MSVC, and
this is the only static library used.