Fixed implicit declaration of memcpy

lab6/lib/list.c

 #include "list.h"
 #include <stdlib.h>
+#include <string.h>
 
 list* create_list() {
 	list* l = (list *)calloc(1, sizeof(list));
@@ -57,4 +58,4 @@ void add_list_elem(list* list, void* info, int info_len, int seq) {
 	}
 
 	list->size++;
-}
\ No newline at end of file
+}