Add missing headerfile for TempNamespaceOidIsValid()

Fixes compiler warning for implicit function declaration in proc.c

src/backend/storage/lmgr/proc.c

@@ -38,6 +38,7 @@
 
 #include "access/transam.h"
 #include "access/xact.h"
+#include "catalog/namespace.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
 #include "replication/syncrep.h"