[MERGE][trivial] Fix a few typos in docstrings

[Matt Nordhoff]

Fix a few typos in docstrings.

I'm not 100% sure about the is_empty changes. I think I'm right, but I
might have it all horribly wrong. Still, the other change is correct,
and they're in separate revisions anyway.
-- 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: typos_200903.patch
Type: text/x-diff
Size: 3851 bytes
Desc: not available
Url : https://lists.ubuntu.com/archives/bazaar/attachments/20090325/2e4eea4b/attachment.bin