Have dist.sh generate subversion.pot for the benefit of translators who need
it in the source distribution.

* tools/dist/dist.sh: Generate subversion.pot by running po-update.sh. 

Patch by: mattiase


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1601496 13f79535-47bb-0310-9956-ffa450edef68