OpenGL: Map Specific Palette Fix

This makes OpenGL stop using a specific function that doesn't really do anything for it anymore. It looks like it was used for a hack that would change the colour of polygons for the flashpal equivalent in DOOM. I made it so ST_DoPaletteStuff doesn't set the flashpal in OpenGL as it already does its own hacky overlay and doing that would cause all the textures to be flushed more mid-level, it could be enabled for more correct flashpals, but they still wouldn't effect fog or lighting. This means the palette will be set when going to the title screen, and twice when starting a map, (causing the OpenGL cached textures to also be flushed at those times)