Add missing header

This commit was SVN r23497.

orte/mca/ess/generic/ess_generic_component.c

@@ -26,6 +26,10 @@
 #include "orte_config.h"
 #include "orte/constants.h"
 
+#ifdef HAVE_STRING_H
+#include <string.h>
+#endif
+
 #include "opal/mca/base/mca_base_param.h"
 
 #include "orte/util/proc_info.h"