GL_ARB_texture_rg
http://www.opengl.org/registry/specs/gl/ARB/texture_rg.txt
GL_ARB_texture_rg
	GL_COMPRESSED_RED 0x8225
	GL_COMPRESSED_RG 0x8226
	GL_RG 0x8227
	GL_RG_INTEGER 0x8228
	GL_R8 0x8229
	GL_R16 0x822A
	GL_RG8 0x822B
	GL_RG16 0x822C
	GL_R16F 0x822D
	GL_R32F 0x822E
	GL_RG16F 0x822F
	GL_RG32F 0x8230
	GL_R8I 0x8231
	GL_R8UI 0x8232
	GL_R16I 0x8233
	GL_R16UI 0x8234
	GL_R32I 0x8235
	GL_R32UI 0x8236
	GL_RG8I 0x8237
	GL_RG8UI 0x8238
	GL_RG16I 0x8239
	GL_RG16UI 0x823A
	GL_RG32I 0x823B
	GL_RG32UI 0x823C