changed Q1BSP traceline to only use the surface-hitting variant if

changed Q1BSP traceline to only use the surface-hitting variant if
sv_gameplayfix_q1bsptracelinereportstexture is on, because in one of
negke's maps a set of items are crushed by a pusher and are expected to
fall through the sky brush they are sitting on, which does not happen if
the sky surface is considered solid, but in any other situation this
should be reported as solid

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@11897 d7cf8633-e32d-0410-b094-e92efae38249