GL_EXT_framebuffer_multisample
http://www.opengl.org/registry/specs/EXT/framebuffer_multisample.txt
GL_EXT_framebuffer_multisample
	GL_RENDERBUFFER_SAMPLES_EXT 0x8CAB
	GL_FRAMEBUFFER_INCOMPLETE_MULTISAMPLE_EXT 0x8D56
	GL_MAX_SAMPLES_EXT 0x8D57
	void glRenderbufferStorageMultisampleEXT (GLenum target, GLsizei samples, GLenum internalformat, GLsizei width, GLsizei height)
	GL_FRAMEBUFFER_INCOMPLETE_MULTISAMPLE_EXT 0x8D56
	GL_MAX_SAMPLES_EXT 0x8D57