A Biosynthetic Control on Structures Serving as Ligands for Selectins: The Precursor Structures, 3-Sialyl/Sulfo Galβ1,3/4GlcNAcβ-0-R, Which Are High Affinity Substrates for α1,3/4-L-Fucosyltransferases, Exhibit the Phenomenon of Substrate Inhibition