In 1.8, post-commit hooks get a third argument (the transaction name).
Update the example svnpubsub post-commit handler to accept and ignore it.

* tools/server-side/svnpubsub/commit-hook.py (at top level):
   Move script configuration constants to the top of the file.
   Accept, and ignore, a fourth command-line argument.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1486457 13f79535-47bb-0310-9956-ffa450edef68