Support --with-revprop in svnmucc.

Support --with-revprop in svnmucc.

* contrib/client-side/svnmucc/svnmucc.c
  (commit_callback): Upgrade to svn_commit_callback2_t interface.
  (execute): Take revprops hash instead of log message argument and pass
    along to svn_ra_get_commit_editor3, not svn_ra_get_commit_editor.
  (usage): Document --with-revprop option.
  (main): Parse --with-revprop option, integrate with log message options,
    and pass along to execute.

* subversion/libsvn_subr/opt.c
  (svn_opt_parse_revprop): Move parse_revprop from subversion/svn/main.c
    here; rename revprop_pair to revprop_spec, as it's not a pair
    of revprops.

* subversion/include/svn_opt.h
  (svn_opt_parse_revprop): Declare.

* subversion/svn/main.c
  (parse_revprop): Remove.
  (main): Use svn_opt_parse_revprop instead of parse_revprop.

git-svn-id: http://svn.collab.net/repos/svn/trunk@29492 612f8ebc-c883-4be0-9ee0-a4e9ef946e3a