[Templates] XS Stash DOES support tied objects... apparently

[Andy Wardley]

Well I'm not quite sure what's going on here, but it appears that the 
XS Stash does indeed have support for tied hashes and arrays, and from the 
look of it, always has.

The problem is that the hash assignment code was broken in a subtle way
so as to make it look like it didn't work.

I think I've fixed the bug, so it looks like we now have full support
for tied objects in the XS Stash.

Yay!

A