Fix properties of literal array initialisers

Fix properties of literal array initialisers

Array entries defined in such a way need to be own properties.
To avoid calling builtin_define_property with the integer index
converted to a string for each property, this patch also introduces
a builtin_define_array_property that takes an integer index instead.

Change-Id: Ib21f99a555b3237753a7930a7edc70bfcd49ac18
Reviewed-by: Lars Knoll <lars.knoll@digia.com>