formed DP_GFX_FONTS/DP_GFX_FONTS_FREETYPE/DP_UTF8 extensions, add loadfont()/findfont...

formed DP_GFX_FONTS/DP_GFX_FONTS_FREETYPE/DP_UTF8 extensions, add loadfont()/findfont() builtins. Font structure is now expandable (grows by 8), so new fonts could be added at no limits, just use new names for loadfont. When loading font, check for given file path before add extensions, this make "loadfont user1 myfont.ttf 10" work correctly.

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@10211 d7cf8633-e32d-0410-b094-e92efae38249
::stable-branch::merge=c2673128f60447e2884d89455ebbcaffbc4f6bb3