Offsetmapping now could be customized on per-texture basis. Added mod_q3shader_defaul...

Offsetmapping now could be customized on per-texture basis. Added mod_q3shader_default_offsetmapping cvar which is 1 by default (offsetmapping is on by default on all surfs), and 0 (only shader-set). New q3shader keyword "dp_offsetmapping <type> <scale>". Typical example: "dp_offsetmapping default 2". Types are "off", "default" (legacy cvar-based behavior), "linear" and "relief". Linear/relief is forced modes that ignores r_glsl_offsetmapping_reliefmapping.

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@9993 d7cf8633-e32d-0410-b094-e92efae38249
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