Fixed EM reels not updating.
Fixed depth bias values to be more reasonable.

This fixes rendering issues on Seawitch.
VP9 compatibility fix: made pure black gates invisible.
apply secondary/backglass sound output patch by DJRobX

git-svn-id: svn://svn.code.sf.net/p/vpinball/code/trunk@923 14438d79-0ffd-4333-8ae7-ea2bdd901387
Removed all calls to enable dithering.
Merge branch 'master' into fixes
Merge branch 'dev' of https://github.com/c-f-h/vpinball into dev
Merge branch 'fixes' into dev

Conflicts:
	vpinball.cpp