PR #33: Fix a bug in mailer.py caused by improper user of dict.update().

* tools/hook-scripts/mailer/mailer.py
  (Config._prep_groups::repos_params): If there's a match for the
   repository configuration, copy the defaults dict and update it
   in place before returning the new dict.

Patch by: humbedooh


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1927075 13f79535-47bb-0310-9956-ffa450edef68