Log Message:
Update mercurial to 0.8.1.

Changes:
- new extensions:
  mq (manage a queue of patches, like quilt only better)
  email (send changes as series of email patches)
- new command: merge (replaces "update -m")
- improved commands: log (--limit option added), pull/push ("-r" works
  on specific revisions), revert (rewritten, much better)
- comprehensive hook support
- output templating added, supporting e.g. GNU changelog style
- Windows, Mac OS X: prebuilt binary packages, better support
- many reliability, performance, and memory usage improvements