renamed nullfunction to SUB_Null and gave it a definition to hush compiler warnings

renamed nullfunction to SUB_Null and gave it a definition to hush compiler warnings
added g_fullbrightitems cvar
removed norespawn field, instead dropped weapons check if their classname is "droppedweapon", and VanishOrRemove (called by SetFade stuff) checks FL_CLIENT (since players are the only thing that fade and can respawn), this fixes a buildup of expired muzzleflash effects (thanks to Spike for reporting this)

git-svn-id: svn://svn.icculus.org/nexuiz/trunk@401 f962a42d-fe04-0410-a3ab-8c8b0445ebaa