Don't bother checking vid_gamma for CVAR_ROM becuase it is impossible to
get to VID_UpdateGamma when it is set except for when the cvar is
initially created, and we /want/ the code to execute in that case.
vid.h:
add initialized to viddef_t
vid_common_gl.c:
actually /use/ gammatable (it tends to help)
vid_*.c:
clean up rendundant decls of gammatable, vid_initialized (now
vid.initialized) and make sure vid.initialized gets set.
gl_view.c:
remove gammatable decls
