-Change R_RenderSegRange to render each wall tier in a separate loop. This is more efficient than rendering a a column from each tier all in one loop.

git-svn-id: http://odamex.net/svn/root/branches/rend32@3932 b0bcef46-2027-0410-bd56-ab726e9a1d04
-Add parameters to R_RenderColumnRange for arrays specifying the top and bottom screen coordinates of each column in the range and an array specifying the tallpost_t* for each column.
-Simplify the solid seg column blaster function. Now the clipping is handled by R_RenderSolidSegRange.

git-svn-id: http://odamex.net/svn/root/branches/rend32@3933 b0bcef46-2027-0410-bd56-ab726e9a1d04
-Change dc_midposts, dc_topposts, and dc_bottomposts to static variables since they're not used outside r_segs.cpp.

git-svn-id: http://odamex.net/svn/root/branches/rend32@3934 b0bcef46-2027-0410-bd56-ab726e9a1d04