Add --force-interactive to svnmucc.

* subversion/svnmucc/svnmucc.c
  (main): Add force-interactive, make non-interactive/force-interactive
   handling behave the same way as the other clients.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1457789 13f79535-47bb-0310-9956-ffa450edef68