fixed a bug in texture generator that made all the particles too large in the particl...

fixed a bug in texture generator that made all the particles too large in the particle font by one pixel (now they're smaller than their frame, like they were supposed to be), this fixes all the sharp edges on particles
changed nexbeam to be quite a bit brighter in the center than the sides (as I really wanted it all along)
nexbeam no longer scrolls its texture (looked odd)

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@4937 d7cf8633-e32d-0410-b094-e92efae38249