Improvements to buildit

1. Filip Pizlo passed on the attached patch which improves ssh handling of the buildit script. Fil, can you please do a "statement of origin" so we can formally contribute it? (http://jikesrvm.org/Contributions)

2. I would also like to switch the -p switch from being perfcounter (which I use, but is esoteric and not used by many), to profile, which everyone should be using for performance studies. Please yell if you don't want me to do this.

3. I have started writing some notes on the wiki on how to use buildit, with a handful of examples.