Fix drawflag handling in Mod_Mesh_GetTexture by duplicating texture_t when drawflag...

Fix drawflag handling in Mod_Mesh_GetTexture by duplicating texture_t when drawflag overrides differ (it still uses the same skinframe_t so it's not duplicating the actual texture).

This fixes a menu issue in Steel Storm: Burning Retribution where the black text over a hover button was being rendered as MATERIALFLAG_ADD due to DRAWFLAG_ADD being used earlier in the frame on the same font image, which made the text invisible.

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@12505 d7cf8633-e32d-0410-b094-e92efae38249