ConditionalRendering

Last Revision:	Version 1.1, 2014-06-17 Updated with Core Profile and GLKit Math Utilities. Moved shader setup to -prepareOpenGL to ensure that the OpenGL framebuffer is valid at the time and thus avoid validation failure. Replaced the NSTimer with a CVDisplayLink to drive the rendering loop. Cleaned up code.
Build Requirements:	OS X v10.9 or later, Xcode 5.0 or later
Runtime Requirements:	OS X v10.7 or later

This sample demonstrates how to do conditional rendering based on an occlusion query. The NV_conditional_render extension defines two functions, BeginConditionalRenderNV and EndConditionalRenderNV, between which rendering commands may be discarded based on the results of an occlusion query. If the specified occlusion query returns a non-zero value, rendering commands between these calls are executed; otherwise, they are all discarded.