[MERGE] More than double the speed of "bzr selftest"

[Andrew Bennetts]

Alexander Belchenko wrote:
[...]
> Andrew, my changes is now in bzr.dev, so you can use special function
> in bzrlib.tests.__init__: _rmtree_temp_dir(dirname) instead of shutil.rmtree()
> for new version of your patch.
> My function provides safe rmtree for our test suite.

Great, thanks!

I'll update my patch in the next day or so.

-Andrew.