revised water shader, less refraction, more focus on reflections

revised water shader, less refraction, more focus on reflections
added MODE_LIGHTMAP shader permutation flag, this simplified the shader
some other cleanup (q3 vertex shaded surfaces should now properly
respond to r_ambient)
implemented internal support for reflection surfaces (as opposed to full
refraction+reflection water effects)

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@7577 d7cf8633-e32d-0410-b094-e92efae38249