support half-float as an image source texture type
Merge pull request #531 from pizthewiz/half-float

support half-float as an image source texture type
initial Param support for Pan2dNode.
implement sample accurate panning
better test code for Pan2dNode::setStereoInputModeEnabled()
fix reversed panning positions in FallingGears sample
Merge remote-tracking branch 'upstream/master' into master-scons