implement thread_set_nice and make skeleton for calculate_priority

src/threads/thread.c

@@ -364,11 +364,20 @@ thread_get_priority (void)
   return thread_current ()->priority;
 }
 
+/* Calculates priority for the current thread */
+int
+calculate_priority (void)
+{
+	/* Not yet implemented */
+	return 0;
+}
+
 /* Sets the current thread's nice value to NICE. */
 void
-thread_set_nice (int nice UNUSED) 
+thread_set_nice (int nice)
 {
-  /* Not yet implemented. */
+  thread_current ()->nice = nice;
+  calculate_priority ();
 }
 
 /* Returns the current thread's nice value. */