Fix an array-bound violation, add some include guards.

include/sys/types.h

@@ -1,3 +1,6 @@
+#ifndef _INC_SYS_TYPE_H
+#define _INC_SYS_TYPE_H
+
 /*
  * this files resolves conflicts between the file of the host system and
  * the minix specific one. This file is included directly only on Minix
@@ -9,3 +12,5 @@
 #else
 #include <minix/types.h>
 #endif
+
+#endif