GL_NV_explicit_multisample
http://www.opengl.org/registry/specs/NV/explicit_multisample.txt
GL_NV_explicit_multisample
	GL_SAMPLE_POSITION_NV 0x8E50
	GL_SAMPLE_MASK_NV 0x8E51
	GL_SAMPLE_MASK_VALUE_NV 0x8E52
	GL_TEXTURE_BINDING_RENDERBUFFER_NV 0x8E53
	GL_TEXTURE_RENDERBUFFER_DATA_STORE_BINDING_NV 0x8E54
	GL_TEXTURE_RENDERBUFFER_NV 0x8E55
	GL_SAMPLER_RENDERBUFFER_NV 0x8E56
	GL_INT_SAMPLER_RENDERBUFFER_NV 0x8E57
	GL_UNSIGNED_INT_SAMPLER_RENDERBUFFER_NV 0x8E58
	GL_MAX_SAMPLE_MASK_WORDS_NV 0x8E59
	void glGetMultisamplefvNV (GLenum pname, GLuint index, GLfloat* val)
	void glSampleMaskIndexedNV (GLuint index, GLbitfield mask)
	void glTexRenderbufferNV (GLenum target, GLuint renderbuffer)
