All strings whose are valid array indicies always use the UINT32_IN_DESC format. (#1422)

This patch reduces memory consumption for strings such as "0" or "123"
by 8 bytes and "4294967295" by 16 bytes. The hash computation is changed
for using the lower 16 bits for these strings which is much faster than
converting the value to string first and compute the hash. The trade-of
is a small overhead when strings are created or concatenated.

JerryScript-DCO-1.0-Signed-off-by: Zoltan Herczeg zherczeg.u-szeged@partner.samsung.com

jerry-core/ecma/operations/ecma-array-object.c

@@ -301,9 +301,9 @@ ecma_op_array_object_define_own_property (ecma_object_t *object_p, /**< the arra
     return ecma_op_array_object_set_length (object_p, property_desc_p->value, flags);
   }
 
-  uint32_t index;
+  uint32_t index = ecma_string_get_array_index (property_name_p);
 
-  if (!ecma_string_get_array_index (property_name_p, &index))
+  if (index == ECMA_STRING_NOT_ARRAY_INDEX)
   {
     return ecma_op_general_object_define_own_property (object_p, property_name_p, property_desc_p, is_throw);
   }