OpenGL attributes and window creation

[capehill]

According to SDL2 documentation, OpenGL attributes should be set before window creation:
https://wiki.libsdl.org/SDL2/SDL_GL_SetAttribute

However, version attributes are set after window creation here:

ioq3/code/sdl/sdl_glimp.c

Line 742 in 8c48475

SDL_GL_SetAttribute( SDL_GL_CONTEXT_PROFILE_MASK, contexts[type].profileMask );

I don't know if this causes problems on any major systems, but for example on AmigaOS 4, OpenGL library is selected based these attributes so this doesn't work properly if version is set afterwards.