Add skipsupercontentsmask parameter to all the collision implementations, this allows...

Add skipsupercontentsmask parameter to all the collision implementations, this allows you to ignore brushes/surfaces matching the specified contents flags, the primary use is ignoring q1bsp sky surfaces which are SUPERCONTENTS_SKY and SUPERCONTENTS_SOLID, since SUPERCONTENTS_SOLID is in the hitsupercontentsmask it will normally block on sky surfaces, but this way it will not if they also have SUPERCONTENTS_SKY set.

Use the new skipsupercontentsmask feature for bouncegrid traces and certain other light traces.

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@12294 d7cf8633-e32d-0410-b094-e92efae38249