-Fix a wall rendering bug introduced in r3933 that caused an extra pixel to occasionally be rendered in each column and visible through certain walls.

git-svn-id: http://odamex.net/svn/root/branches/rend32@3942 b0bcef46-2027-0410-bd56-ab726e9a1d04
-Increase the NEARCLIP constant for a little added protection against overflows.

git-svn-id: http://odamex.net/svn/root/branches/rend32@3943 b0bcef46-2027-0410-bd56-ab726e9a1d04
-Fix a light calculation issue with the cache-friendly seg drawer code.

git-svn-id: http://odamex.net/svn/root/branches/rend32@3944 b0bcef46-2027-0410-bd56-ab726e9a1d04