Woot... framebuffer objects are working... lotsa multipass and other techniques possible now.  Also added fb discard which got back 10% gpu time.  Added cute Apple gl debugging markers... which are vnice.  Converted more unsightly stl iterations to range for loops.  Fixed bug that didn't clear fb dirty, causing lots of fb rebuilds.  Still haven't tested rt cube maps, but don't have a good scene for that yet.