Changes

Bug 1202: Fix vsync regression on OSX when using CALayer
On OSX using CALayer for onscreen rendering, the drawable is utilizing
an offscreen FBO.
Hence we need to move the vsync-skip-operation criteria, i.e. skip if
offscreen, down to the implementation.

Bug 1212 - OSX: Crash using CALayer at UnsetJAWTRootSurfaceLayer0(..) w/
Java 1.8.0_60
- OSX 10.10.5
- Java 1.8.0_60
Crash using CALayer at UnsetJAWTRootSurfaceLayer0(..) as called within
MacOSXJAWTWindow.invalidateNative() (caller: destroy()) on the
MainThread.
It has been observed that the JAWT_SurfaceLayers protocol instance
'surfaceLayers' has been pulled beforehand.
'surfaceLayers' is fetched from the locked JAWT instance via
JAWT_DrawingSurfaceInfo's platformInfo.
It now seems required to retain the instance at
GetJAWTSurfaceLayersHandle0 and release it at UnsetJAWTRootSurfaceLayer0
to keep it alive.
+++
Manually executed 'ant junit.run' on OSX, no failures or errors.