[MERGE][#124325] Rename the .bzr.backup dir to .backup.bzr

[Ian Clatworthy]

Ian Clatworthy has voted approve.
Status is now: Conditionally approved
Comment:
I'm ok with this being .backup.bzr. As long as John doesn't feel 
strongly about using a different name, I'll merge this.

For details, see: 
http://bundlebuggy.aaronbentley.com/request/%3C2422be180803040403y6873e4f0pa7fffe32551a12a1%40mail.gmail.com%3E