Fix otherwise unset fragment alpha with VERTEX_COLOR defined.
Check built-in preprocessor macros to see if highp is available
Nullify second object in CollisionPair before notifying listeners after removal

By the time CollisionListener::collisionEvent is called, second object
in the CollisionPair is already deleted and points to an invalid memory
location.
Merge pull request #1373 from rgngl/alphaFix

Fix otherwise unset fragment alpha with VERTEX_COLOR defined.
Merge pull request #1376 from rgngl/shaderPrecisionFix

Check built-in preprocessor macros to see if highp is available
Merge pull request #1377 from rgngl/physicsRemoveFix

Nullify second object in CollisionPair before notifying listeners after removal
Merge branch 'next' of https://github.com/blackberry/GamePlay into next