* Get a fresh window surface before rendering to it
It is possible that a window surface gets invalidated since we initially
obtained it. We need to call GetWindowSurface every time we want one,
instead of keeping a pointer to a possibly stale one.
See https://hg.libsdl.org/SDL/file/369b01006eb2/src/video/SDL_video.c#l2312Fixes#351
Adds a USE_SDL1 build option to use SDL v1 instead of v2.
This is useful for porting Diablo on devices that don't support SDL2,
such as the RetroFW / OpenDingux devices (e.g. RG300 Retro Gaming Handheld)
Not yet supported:
* Fullscreen
* Upscaling
* Audio
Gleb Mazovetskiy
Anders Jenbo