Fix arbitrary sized polygon tex coord generation to actually work.
Fix arbitrary sized polygon tex coord generation to actually work.

This was old code copied from TAGL, where it was using the old gl_polygon
polygon and sequential tex coords. Since we are now using a triangle fan,
the texture coordinates needed to be updated.

Christof-Sigel/TA_SDL,Christof-Sigel/TA_SDL,Christof-Sigel/TA_SDL,Christof-Sigel/TA_SDL