Since I find myself having to write the same code over and again,
since the XSLT WG decided that wherever a URI was expected, an IRI
could be substituted, I prpose adding make_resolve_iri_reference
to UT_URI as a creation routine.
This would be the same as make_resolve, except the precondition of
a_reference_valid: not Url_encoding.has_excluded_characters (a_reference)
would be removed.
Instead, it would test for this condition, and carry out the necessary
precent-escaping if it was not met.