Remove a '__main__' handler from __init__.py.

sql lexer: Add temporal support keywords

Fix #1247 by looking up in both HKLM and HKCU.

* Fix an issue raised in the review -- don't raise None no matter what.
* Remove a few variables to make the control flow easier to understand

This is slightly different from the code posted inside the issue:
* Use finally to close the registry key no matter what
* Don't use break, but return directly on the first hit

This fixes three test failures on Windows:
* Two due to incorrect handling of : (on Windows, multiple : can
  be part of a path.)
* One due to newline differences

SQL:2011 introduced support for temporal databases[1] via new keywords to
create and manage temporal tables. This patchset adds these new keywords to
the sql lexer.

One concrete example of these feature is the temporal tables support in
MariaDB[2]. As evident from the code listing on that page, the syntax
highlighting for these keywords is not as widespread as expected (I wouldn't
be surprised if code listing on that page ultimately use pygments for syntax
highlighting !)

[1] https://en.wikipedia.org/wiki/SQL:2011
[2] https://mariadb.com/kb/en/temporal-data-tables/

Put it into a new category, Keyword.Removed, so it's not completely
gone.