add missing header

This commit was SVN r28897.

ompi/mca/rte/pmi/rte_pmi_db.c

@@ -18,6 +18,7 @@
 #endif
 
 #include "opal/util/argv.h"
+#include "opal/util/output.h"
 #include "opal/dss/dss.h"
 #include "opal/threads/tsd.h"
 #include "opal/mca/hwloc/hwloc.h"