Add context info to OAT_POST_CREATE security hook

... and have sepgsql use it to determine whether to check permissions
during certain operations.  Indexes that are being created as a result
of REINDEX, for instance, do not need to have their permissions checked;
they were already checked when the index was created.

Author: KaiGai Kohei, slightly revised by me

src/backend/commands/tablecmds.c

@@ -630,7 +630,8 @@ DefineRelation(CreateStmt *stmt, char relkind, Oid ownerId)
 										  stmt->oncommit,
 										  reloptions,
 										  true,
-										  allowSystemTableMods);
+										  allowSystemTableMods,
+										  false);
 
 	/* Store inheritance information for new rel. */
 	StoreCatalogInheritance(relationId, inheritOids);