add exercise of lab5 spoc discussion

related_info/lab5/lab5-spoc-discuss/libs/stdlib.h

@@ -0,0 +1,17 @@
+#ifndef __LIBS_STDLIB_H__
+#define __LIBS_STDLIB_H__
+
+#include <defs.h>
+
+/* the largest number rand will return */
+#define RAND_MAX    2147483647UL
+
+/* libs/rand.c */
+int rand(void);
+void srand(unsigned int seed);
+
+/* libs/hash.c */
+uint32_t hash32(uint32_t val, unsigned int bits);
+
+#endif /* !__LIBS_RAND_H__ */
+