Added some inclusions of string.h where necessary.

diff --git a/scheduler/pthread.c b/scheduler/pthread.c
index fb17555..9af6b31 100644
--- a/scheduler/pthread.c
+++ b/scheduler/pthread.c
@@ -14,6 +14,7 @@
 #include <errno.h>
 #include <stdlib.h>
 #include <unistd.h>
+#include <string.h>
 
 #include "winbase.h"
 #include "thread.h"