Port EDuke32's 8-bit classic-accurate OpenGL shading, visibility, and fog.

usenewshading 1 by Helixhorned and TerminX
usenewshading 2 by Helixhorned
usetileshades by TerminX
usetileshades polymosttex port by Hendricks266
Implement "tilefromtexture" def command and all required components.