Fix warings while making html-en

I'm not sure why core-libraries/components/email was excluded.

Also there's still one warning:
./en/development/debugging.rst:13: WARNING: duplicate object description of debug, other instance in ./en/core-libraries/global-constants-and-functions.rst

The recommended way to avoid it is to add :noindex:, but it doesn't work for some reason.
https://groups.google.com/forum/#!topic/sphinx-users/lzQEf7Jswgg