GL_ARB_draw_buffers
http://oss.sgi.com/projects/ogl-sample/registry/ARB/draw_buffers.txt
	GL_MAX_DRAW_BUFFERS_ARB 0x8824
	GL_DRAW_BUFFER0_ARB 0x8825
	GL_DRAW_BUFFER1_ARB 0x8826
	GL_DRAW_BUFFER2_ARB 0x8827
	GL_DRAW_BUFFER3_ARB 0x8828
	GL_DRAW_BUFFER4_ARB 0x8829
	GL_DRAW_BUFFER5_ARB 0x882A
	GL_DRAW_BUFFER6_ARB 0x882B
	GL_DRAW_BUFFER7_ARB 0x882C
	GL_DRAW_BUFFER8_ARB 0x882D
	GL_DRAW_BUFFER9_ARB 0x882E
	GL_DRAW_BUFFER10_ARB 0x882F
	GL_DRAW_BUFFER11_ARB 0x8830
	GL_DRAW_BUFFER12_ARB 0x8831
	GL_DRAW_BUFFER13_ARB 0x8832
	GL_DRAW_BUFFER14_ARB 0x8833
	GL_DRAW_BUFFER15_ARB 0x8834
	void glDrawBuffersARB (GLsizei n, const GLenum* bufs)