Module framebuffer

Warning: Framebuffers are currently bound for drawing only (GL_DRAW_FRAMEBUFFER, not GL_READ_FRAMEBUFFER).

To Do:

• Implement binding for reading; wrap glReadPixels, glBlitFramebuffer, glCopyTexSubImage and related framebuffer copy functions.
• Add properties for viewport, color_writemask, depth_writemask, blend_func, blend_equation, and depth_range (using glDepthRangeArray and glDepthRangeIndexed).

Author: Stephan Wenger

Date: 2012-02-29