Provide a RegexListOutput class in the test suite to match a list of regular
expressions.

See the dev@ email thread '[PATCH] Support regex in EXPECTED ERR list'
starting 2013-01-23, e.g. <http://svn.haxx.se/dev/archive-2013-01/0433.shtml>
or <http://mail-archives.apache.org/mod_mbox/subversion-dev/201301.mbox/%3C50FF938A.9040007%40collab.net%3E>.

* subversion/tests/cmdline/svntest/verify.py
  (RegexListOutput): New class.
  (ExpectedOutput, UnorderedRegexOutput): Tweak comments.

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1443718 13f79535-47bb-0310-9956-ffa450edef68