Escape backslashes

[clalancette]

When running on Windows Debug (where all warnings are printed), the backslashes in these strings/comments were causing warnings like:

C:\J\workspace\nightly_win_deb\ws\install\Lib\site-packages\ament_cpplint\cpplint.py:1110: DeprecationWarning: invalid escape sequence \D

In cpplint.py, escape the backslashes properly (since these are triple-quoted strings). In cmakelint.py, make the strings raw.

[clalancette]

Debug CI; these warnings no longer exist there: https://ci.ros2.org/job/ci_windows/7142/

[dirk-thomas]

Both changed files are imported versions of upstream projects. Please file PRs against upstream first and once those have been accepted we can pull their latest version into this repo.

[clalancette]

I've opened richq/cmake-lint#36 and google/styleguide#455

That being said, I won't hold my breath for either them to be merged. There have been no accepted changes to upstream cmake-lint since 2017, and the author has said he isn't really interested in it anymore: https://github.com/richq/cmake-lint/issues/29#issuecomment-431682169

The Google styleguide is slightly more active, but after 4 years they still haven't merged the python3 support patch that we are currently relying on: google/styleguide#47

[dirk-thomas]

Please revert the unrelated whitespace changes from this PR. Then I think we can merge this without squashing. 👍

[clalancette]

Please revert the unrelated whitespace changes from this PR. Then I think we can merge this without squashing. +1

Rebased and done.

[clalancette]

CI was done as part of ros2/ci#301, and was successful, so I'll merge this.