this patch adds a number of stereo viewing modes (shutter glasses and video glasses...

this patch adds a number of stereo viewing modes (shutter glasses and video glasses not supported yet)
added r_stereo_redblue and r_stereo_redgreen and r_stereo_redcyan (anaglyph 3d glasses)
added r_stereo_sidebyside (no glasses, recommend using the smallest viewsize to get them lined up with your eyes, then stare straight ahead...  warning: eye strain)
added r_stereo_separation (sets how far apart the eyes are in the world, default is 4 units, technically this should be 1.33, about 2 inches, but the quake player is a midget compared to the world...  so that doesn't look right)

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@4299 d7cf8633-e32d-0410-b094-e92efae38249