-Remove some unnecessary checks in R_CheckProjectionX and R_CheckProjectionY.

git-svn-id: http://odamex.net/svn/root/branches/rend32@4116 b0bcef46-2027-0410-bd56-ab726e9a1d04
-Check each of the four sides of a BSP node bounding box for visibility before rejecting the node.
-Checking the two diagonals of a bounding box for visibility was not sufficient in a few rare cases (entryway of memorial.wad).

git-svn-id: http://odamex.net/svn/root/branches/rend32@4117 b0bcef46-2027-0410-bd56-ab726e9a1d04
-Merge from trunk into rend32.

git-svn-id: http://odamex.net/svn/root/branches/rend32@4118 b0bcef46-2027-0410-bd56-ab726e9a1d04