GL_SGIS_texture_lod
http://www.opengl.org/registry/specs/SGIS/texture_lod.txt
	GL_TEXTURE_MIN_LOD_SGIS 0x813A
	GL_TEXTURE_MAX_LOD_SGIS 0x813B
	GL_TEXTURE_BASE_LEVEL_SGIS 0x813C
	GL_TEXTURE_MAX_LEVEL_SGIS 0x813D
