Code to hopefully support Flash in Internet Explorer in Windows 8 once the new versio...

Code to hopefully support Flash in Internet Explorer in Windows 8 once the new version of Flash is released.
Unfortunately, I can't actually test this as I don't have access to this new version for Windows 8 IE yet.
I'm merging this code now because it'd be good to have this support in 2013.1, it doesn't make things any worse than they are now and there are significant changes which may affect other versions of Flash which need further testing, though my testing hasn't revealed any problems.
Fixes #2454.