GL_ARB_multisample
http://oss.sgi.com/projects/ogl-sample/registry/ARB/multisample.txt
	GL_MULTISAMPLE_ARB 0x809D
	GL_SAMPLE_ALPHA_TO_COVERAGE_ARB 0x809E
	GL_SAMPLE_ALPHA_TO_ONE_ARB 0x809F
	GL_SAMPLE_COVERAGE_ARB 0x80A0
	GL_SAMPLE_BUFFERS_ARB 0x80A8
	GL_SAMPLES_ARB 0x80A9
	GL_SAMPLE_COVERAGE_VALUE_ARB 0x80AA
	GL_SAMPLE_COVERAGE_INVERT_ARB 0x80AB
	GL_MULTISAMPLE_BIT_ARB 0x20000000
	void glSampleCoverageARB (GLclampf value, GLboolean invert)