Change many routines to return ObjectAddress rather than OID

The changed routines are mostly those that can be directly called by
ProcessUtilitySlow; the intention is to make the affected object
information more precise, in support for future event trigger changes.
Originally it was envisioned that the OID of the affected object would
be enough, and in most cases that is correct, but upon actually
implementing the event trigger changes it turned out that ObjectAddress
is more widely useful.

Additionally, some command execution routines grew an output argument
that's an object address which provides further info about the executed
command.  To wit:

* for ALTER DOMAIN / ADD CONSTRAINT, it corresponds to the address of
  the new constraint

* for ALTER OBJECT / SET SCHEMA, it corresponds to the address of the
  schema that originally contained the object.

* for ALTER EXTENSION {ADD, DROP} OBJECT, it corresponds to the address
  of the object added to or dropped from the extension.

There's no user-visible change in this commit, and no functional change
either.

Discussion: 20150218213255.GC6717@tamriel.snowman.net
Reviewed-By: Stephen Frost, Andres Freund

src/include/rewrite/rewriteDefine.h

@@ -14,6 +14,7 @@
 #ifndef REWRITEDEFINE_H
 #define REWRITEDEFINE_H
 
+#include "catalog/objectaddress.h"
 #include "nodes/parsenodes.h"
 #include "utils/relcache.h"
 
@@ -22,9 +23,9 @@
 #define RULE_FIRES_ON_REPLICA	'R'
 #define RULE_DISABLED			'D'
 
-extern Oid	DefineRule(RuleStmt *stmt, const char *queryString);
+extern ObjectAddress DefineRule(RuleStmt *stmt, const char *queryString);
 
-extern Oid DefineQueryRewrite(char *rulename,
+extern ObjectAddress DefineQueryRewrite(char *rulename,
 				   Oid event_relid,
 				   Node *event_qual,
 				   CmdType event_type,
@@ -32,7 +33,7 @@ extern Oid DefineQueryRewrite(char *rulename,
 				   bool replace,
 				   List *action);
 
-extern Oid RenameRewriteRule(RangeVar *relation, const char *oldName,
+extern ObjectAddress RenameRewriteRule(RangeVar *relation, const char *oldName,
 				  const char *newName);
 
 extern void setRuleCheckAsUser(Node *node, Oid userid);