[IronPython] Thread local storage in IronPython 2.6

[Dino Viehland]

Michael wrote:
> Cool. If it becomes a problem then we'll get in touch and see how we can
> mitigate against it.
> 
> At the top level you could put all the cleanup code inside a finally
> block so that thread aborts can't interrupt it. :-)

Somehow I guess I'd quickly get a bug report that Ctrl-C no longer works 
too :)  But there's a kernel of a good idea there - it's certainly 
easier than using Constrained Execution Regions which was my longer 
term plan (and also has trouble w/ partial trust unlike a normal
try/finally).