Introduce PassPhraseDialog 'pipe' mechanism.  This builds on DougM's
  apr-ization of the 'tty', and changes his naming a bit so we clearly
  identify the pipe-to and pipe-from the user.

  This patch invokes a bidirectional piped dialog to the user.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@93607 13f79535-47bb-0310-9956-ffa450edef68