[IronPython] pybench results for CPython and IronPython

[Arman Bostani]

I assume that IronPython is implemented with thread-safe data structures 
(i.e. there's no GIL).  If so, then IronPython is at a disadvantage on 
single-threaded benchmarks like pybench.

Just for fun, I tested System.Collections.SortedList against its thread 
safe (Synchronized) version.  The latter was 5 times slower!

In light of this simple test, its possible that 1) IP is very efficient 
at implementing thread safety 2) .NET Synchronized collections are 
horribly slow 3) my assumption on IP's implementation are wrong.

-arman