Don't look for best IBSP surfaceNums by default (it's too slow)

Enable cm_betterIbspSurfaceNums to find better surface numbers. It's only needed for (new Spearmint) trap_R_SetSurfaceShader, not worth the extra load time when the trap isn't even used by default.
Also, don't look for draw surface numbers at all in BSPC.
Make Travis CI build BSPC
Fix building BSPC using clang and mingw
Fix some clang warnings in BSPC
Fix mingw warnings in BSPC
Fix clang warning in gl1 ParseFoliage

Clang was warning that foliage->indexes[ i ] < 0 was always false, indexes was unsigned. Changed to int like triangle surface code.
Make UI_BuildServerDisplayList argument an int

It was qboolean, but 2 is used. Clang was warning about it on Travis CI.
Merge remote-tracking branch 'spearmint/master'