Don't render side ramp walls if their height is 0. This can give you a big 
speed improvement if you have a lot of alpha flashers.

git-svn-id: svn://svn.code.sf.net/p/vpinball/code/trunk@623 14438d79-0ffd-4333-8ae7-ea2bdd901387
don't render the other side of the side walls too if left/right wall visible is 0

git-svn-id: svn://svn.code.sf.net/p/vpinball/code/trunk@624 14438d79-0ffd-4333-8ae7-ea2bdd901387
fix small copy/paste error with right wall height

git-svn-id: svn://svn.code.sf.net/p/vpinball/code/trunk@625 14438d79-0ffd-4333-8ae7-ea2bdd901387
some leftovers from last experiments

git-svn-id: svn://svn.code.sf.net/p/vpinball/code/trunk@626 14438d79-0ffd-4333-8ae7-ea2bdd901387
check for left/right visible ramp wall fixed

git-svn-id: svn://svn.code.sf.net/p/vpinball/code/trunk@627 14438d79-0ffd-4333-8ae7-ea2bdd901387
change adaptive vsync code to take user suggestion for targeted refresh rate

git-svn-id: svn://svn.code.sf.net/p/vpinball/code/trunk@628 14438d79-0ffd-4333-8ae7-ea2bdd901387