GL_ARB_blend_func_extended
http://www.opengl.org/registry/specs/gl/ARB/blend_func_extended.txt
GL_ARB_blend_func_extended
	GL_SRC1_COLOR 0x88F9
	GL_ONE_MINUS_SRC1_COLOR 0x88FA
	GL_ONE_MINUS_SRC1_ALPHA 0x88FB
	GL_MAX_DUAL_SOURCE_DRAW_BUFFERS 0x88FC
	void glBindFragDataLocationIndexed (GLuint program, GLuint colorNumber, GLuint index, const GLchar * name)
	GLint glGetFragDataIndex (GLuint program, const GLchar * name)