Add validate-files.py, a python pre-commit hook-script that runs commands and
rejects commits if the command does not exit with a 0 exit code.

* tools/hook-scripts/validate-files.py: The hook-script itself.

* tools/hook-scripts/validate-files.conf.example: Example conf file.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1429235 13f79535-47bb-0310-9956-ffa450edef68