Add a hook script that rejects filenames that contain control characters.

This is needed at least for filenames that contain newlines;
tools/hook-scripts/validate-files.py can't handle those since svnlook's output
is not parseable in that case.

Thread: http://mid.gmane.org/CADkdwvRfkX=-b_wb8S-NqUD3r9V=omdHqd9eOX0iumuojRM0og@mail.gmail.com

Patch by: breser

* tools/hook-scripts/control-chars.py: New script.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1461389 13f79535-47bb-0310-9956-ffa450edef68