[SDL] Hide ouput of the SDL_SetVideoMode

[Ken Phillis]

I'm wondering if by SDL version 1.3 a new flag can be added to the
setvideo mode such that one can do all the output in a frame or other
application like this example:
http://code.technoplaza.net/wx-sdl/part1
without having a background window come up that isn't being used at
all, and do all the work in just the sdl surfaces with an output
frame.

a new flag to go with the two existing flags, SDL_RESIZABLE and SDL_NOFRAME ...

I'd suggest adding the flag, SDL_NOVIDEOOUTPUT for these type of circumstances.