GL_NV_framebuffer_multisample
http://www.opengl.org/registry/specs/NV/framebuffer_multisample.txt
GL_NV_framebuffer_multisample

	GL_RENDERBUFFER_SAMPLES_NV 0x8CAB
	GL_FRAMEBUFFER_INCOMPLETE_MULTISAMPLE_NV 0x8D56
	GL_MAX_SAMPLES_NV 0x8D57
	void glRenderbufferStorageMultisampleNV (GLenum target, GLsizei samples, GLenum internalformat, GLsizei width, GLsizei height)