GL_ARB_texture_swizzle
http://www.opengl.org/registry/specs/ARB/texture_swizzle.txt
GL_ARB_texture_swizzle
	GL_TEXTURE_SWIZZLE_R 0x8E42
	GL_TEXTURE_SWIZZLE_G 0x8E43
	GL_TEXTURE_SWIZZLE_B 0x8E44
	GL_TEXTURE_SWIZZLE_A 0x8E45
	GL_TEXTURE_SWIZZLE_RGBA 0x8E46
