Fix some typos in configs/messages

Detected by misspellings tool:

* pip install misspellings
* git ls-files | grep -v locale | misspellings -f -

Change-Id: I8911de510d23f926085ec6e96577854de6fa52da
Sync requirements: pin Sphinx to <1.2

1.2 was just released and has a bug that causes builds to fail with
the error:

  error: 'source_dir' must be a directory name (got `...doc/source`)

See:

http://bugs.python.org/issue19570
https://bitbucket.org/birkenfeld/sphinx/pull-request/193/builddoc-shouldnt-fail-on-unicode-paths/diff

Change-Id: I45c59b30b0afd6be8ce94390042f5e75534046bd
Merge "Fix some typos in configs/messages"