Upgrade to Bazaar 2.1.x on Windows

[Adrian Wilkins]

> trouble with plugins

In addition to the issues Alexander mentions, the current 2.1.0-2 installer
packages a version of the xmloutput plugin that doesn't work with bzr 2.1
due to the way it handles output.

This means that software that depends on it like the Eclipse plugin will 
fail.

You can work around this one by pulling the tip of the development branch
for bzr-xmloutput into your plugins folder.