regressions: Add missing include for memset.

Signed-off-by: Samy Al Bahra <sbahra@appnexus.com>

regressions/ck_pr/benchmark/benchmark.h

@@ -5,6 +5,7 @@
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 #include <strings.h>
 #include <unistd.h>
 #include <sys/time.h>

regressions/ck_spinlock/benchmark/throughput.h

@@ -31,6 +31,7 @@
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 #include <strings.h>
 #include <unistd.h>
 #include <sys/time.h>