Test for seg fault on NSKeyedArchiver with arrays of larger size

This reproduces a SIGSEGV when using NSKeyedArchiver to serialize an array of objects that implement NSCoding.  Changing **const int iters = 253;** to anything less will not give a segmentation fault.

I haven't really dug in to the issue, but Paul Beusterien mentioned it might be related to the key size growing from one byte to two when the size of the archive increases.

I am running this against 12fe3692a5 on apportable/master.  This was not an issue when using the old GNUStep based foundation.