-Change usage of 'render' to 'display' in D_RunTics. The entire visual display is being updated, not just the rendered scene.

git-svn-id: http://odamex.net/svn/root/trunk@4470 b0bcef46-2027-0410-bd56-ab726e9a1d04
-Fix a bug calculating the position between simulation frames for render interpolation when the simulation function has to be called more than 4 times in a row.

git-svn-id: http://odamex.net/svn/root/trunk@4471 b0bcef46-2027-0410-bd56-ab726e9a1d04