Cleanup of vsDisplayList

Removes OpCode_MoveTo and OpCode_LineTo (which haven't worked for
years), and several other unused functions.
Removes commented-out "SetDrawMode" render command.
General code cleanup
Removes unused header.
General OpenGL cleanups, moving OGL code to renderer.

Also, removes some more old rendering commands.  Moves 'DrawPoint' to
'Points', removing the last vestige of OpenGL 1.2 code.