Fix (performance improvements) for pixelperfect collision on non-Flash targets (hopefully resolves #769)
Added @crazysam optimizations to avoid unnecessary allocations (except for the BMD cache)
Changes/optimizations to pixel perfect collision code (now unified for all targets), added FlxBitmapDataPool class for fast retrieving of temp BitmapData
Merge pull request #786 from azrafe7/hotfix/pixelperfect-collision

Hotfix/pixelperfect collision (should resolve #769)