MacOSXCGLContext: Remove Debug output
OSX/NEWT: NSWindow/NSView Ops on main-thread w/o blocking - Part2

Continues commit 81cbcdc8469143587b2044661dd613c798ae02ba

Perform on main-thread invocation from Java, allowing to issue
visibleChanged(..) after creation/visible calls.

This fixes the 'Visibility not reached ..' regressions.