More Travis changes :) Use SDL2 in all builds now.

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@12092 d7cf8633-e32d-0410-b094-e92efae38249
::stable-branch::merge=9a2612ff0270451436ef081994bb20dcb4299916
Disable SDLmain.m for SDL2.

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@12093 d7cf8633-e32d-0410-b094-e92efae38249
::stable-branch::merge=45f4690471d588436f2033dc5af008d40d57b36b