implemented a fixed function fallback for water, but it is disabled

implemented a fixed function fallback for water, but it is disabled
because of extreme distortion artifacts (it would need to use a cubemap
for perspective correction)
implemented two-pass rendering of water and refraction surfaces, this
enables blendfunc of the first layer to work properly, the old path is
still present but disabled

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@7638 d7cf8633-e32d-0410-b094-e92efae38249