Tweak find_composite_type_dependencies API a bit more.

Per discussion with Noah Misch, the previous coding, introduced by
my commit 65377e0b9c on 2011-02-06,
was really an abuse of RELKIND_COMPOSITE_TYPE, since the caller in
typecmds.c is actually passing the name of a domain.  So go back
having a type name argument, but make the first argument a Relation
rather than just a string so we can tell whether it's a table or
a foreign table and emit the proper error message.

src/include/commands/tablecmds.h

@@ -53,7 +53,8 @@ extern void RenameRelationInternal(Oid myrelid,
 					   Oid namespaceId);
 
 extern void find_composite_type_dependencies(Oid typeOid,
-								 char origRelkind, const char *origRelname);
+								 Relation origRelation,
+								 const char *origTypeName);
 
 extern AttrNumber *varattnos_map(TupleDesc olddesc, TupleDesc newdesc);
 extern AttrNumber *varattnos_map_schema(TupleDesc old, List *schema);