Allow MixedArray::MakeReserveLike to work on arrays with virtual size

Previously this would try to create an array with 2^32 elements, causing
an assertion or crash. array_map.hhas calls NewLikeArrayL on arbitrary
input, which in turn calls MixedArray::MakeReserveLike. So any array
originating from EZC would crash when fed into array_map().

Added test case which previously crashed.