REASSIGN OWNED lacks support for FDWs

As per http://archives.postgresql.org/pgsql-general/2012-02/msg00304.php
there is no switch case in shdepReassignOwned for foreign data wrappers.

The obvious short-term answer (and probably the only back-patchable one)
is to add a case for that object type.  But after all the refactoring
that's been done in the general area of this type of command, I'm a bit
surprised that shdepReassignOwned still looks like this.  Can't we merge
this knowledge into someplace where it doesn't have to be maintained
separately?
        regards, tom lane