Fix R_InitExtraColormaps reporting 6 or more colormaps every time you loaded...

Fix R_InitExtraColormaps reporting 6 or more colormaps every time you loaded the game, even though we haven't used C_START/C_END in more than a decade now

Note to self: W_ functions are awfully confusing with returning with LUMPERROR or INT16_MAX. Should sort out what's going on there if necessary