Initial and very rough support for automatic pager for the blame, diff and help
commands.

* subversion/svn/util.c
  (): pull in necessary headers.
  (svn_cl__start_pager, svn_cl__close_pager): New

* subversion/svn/cl.h
  (svn_cl__start_pager, svn_cl__close_pager): New

* subversion/svn/blame-cmd.c
  (svn_cl__blame): Add support for automatic pager.

* subversion/svn/diff-cmd.c
  (svn_cl__diff): Add support for automatic pager.

* subversion/svn/help-cmd.c
  (svn_cl__help): Add support for automatic pager.

Patch by: stsp
(from https://mail-archives.apache.org/mod_mbox/subversion-dev/201402.mbox/%3C20140203200233.GA29698%40jim.stsp.name%3E with changelog by me)


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/automatic-pager@1564998 13f79535-47bb-0310-9956-ffa450edef68