Fix big ineficciency in regobj.search/match (introduced by Barry in an

Fix big ineficciency in regobj.search/match (introduced by Barry in an
otherwise laudible attempt to rationalize the argument parsing): it
would save a copy of the original string instead of a reference to it.
Go back to saving a reference, but keep the "s#" format (using a hack
that involves two argument parsing steps, first using "O", then using
"s#").