Introduce JERRY_UNUSED() instead of __attr_unused___

JerryScript-DCO-1.0-Signed-off-by: Zsolt Borbély zsborbely.u-szeged@partner.samsung.com

tests/unit/test-heap.c

@@ -69,8 +69,7 @@ test_heap_give_some_memory_back (jmem_free_unused_memory_severity_t severity)
 } /* test_heap_give_some_memory_back */
 
 int
-main (int __attr_unused___ argc,
-      char __attr_unused___ **argv)
+main ()
 {
   TEST_INIT ();