Flip cursor images in a copy buffer, not the user buffer
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Made VBOTracker and StateStack package private
fix: IsFullscreen -> isFullscreen - to much c/c++ coding :(
add: IsFullScreen fix: better error message on assertion failure
remove unneded import
Native cursors now have same origin as OpenGL, lower left corner
Added buffer positions to Cursor
Fixed a negative focus feedback loop
Implemented safe VBO indices (phew)
