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/indexcmds.c

@@ -596,7 +596,7 @@ DefineIndex(IndexStmt *stmt,
 					 stmt->isconstraint, stmt->deferrable, stmt->initdeferred,
 					 allowSystemTableMods,
 					 skip_build || stmt->concurrent,
-					 stmt->concurrent);
+					 stmt->concurrent, !check_rights);
 
 	/* Add any requested comment */
 	if (stmt->idxcomment != NULL)