modified gamma handling, now VID_UpdateGamma is only called from VID_Finish, and...

modified gamma handling, now VID_UpdateGamma is only called from VID_Finish, and VID_SetGamma/VID_GetGamma/VID_UpdateGamma take rampsize parameters
VID_UpdateGamma now supports ramp sizes other than 256, and automatically allocates memory accordingly, this allows hardware gamma on X11 to work on Quadro cards (which report 1024 gamma entries according to div0), and allows any other platform to do whatever it wishes

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@6200 d7cf8633-e32d-0410-b094-e92efae38249