Rewrite GetInt syscall

code/userprog/consoledriver.h

@@ -19,7 +19,7 @@ class ConsoleDriver:dontcopythis {
 	void PutString(const char *s); // Behaves like fputs(3S)
 	void GetString(char *s, int n); // Behaves like fgets(3S)
     void PutInt(int n);
-    int GetInt();
+    void GetInt(int * n);
   private:
 	Console *console;
 };