-Don't record dc_yl and dc_yh when using the ZDoom cache-friendly column drawer (r_columnmethod 1) if the column has zero pixels.

git-svn-id: http://odamex.net/svn/root/branches/rend32@3977 b0bcef46-2027-0410-bd56-ab726e9a1d04
-Merge from trunk into rend32.

git-svn-id: http://odamex.net/svn/root/branches/rend32@3980 b0bcef46-2027-0410-bd56-ab726e9a1d04
-Merge from trunk into rend32.
-Fix an actor position interpolation bug.

git-svn-id: http://odamex.net/svn/root/branches/rend32@3982 b0bcef46-2027-0410-bd56-ab726e9a1d04