Removed "low precision" span drawer engine.

git-svn-id: http://mancubus.net/svn/hosted/eternity/trunk@2825 86ba831e-150c-0410-ab35-e06eaae15ed9
Remove lptex64 hack in do_draw_plane

git-svn-id: http://mancubus.net/svn/hosted/eternity/trunk@2826 86ba831e-150c-0410-ab35-e06eaae15ed9
Minus one more option nobody needs.

git-svn-id: http://mancubus.net/svn/hosted/eternity/trunk@2827 86ba831e-150c-0410-ab35-e06eaae15ed9
Seems to fix ConSiGno's loss of interpolation after non-blocking screenwipes.

git-svn-id: http://mancubus.net/svn/hosted/eternity/trunk@2830 86ba831e-150c-0410-ab35-e06eaae15ed9