Make 'svn' print a summary of conflicts before starting interactive
conflict resolution, as well as after resolution is finished, to give the
user an idea of how much resolution work will be needed.

Addresses issue #3497, "auto merge as much as can; then print summary, then
go into conflict resolution".

* subversion/svn/cl.h,
  subversion/svn/notify.c
  (svn_cl__notifier_print_conflict_stats): Rewrite as a wrapper ...
  (svn_cl__print_conflict_stats): ... around this new function.

* subversion/svn/conflict-callbacks.c
  (svn_cl__interactive_conflict_baton): Add a flag to remember whether we
    have printed the summary yet.
  (svn_cl__get_conflict_func_interactive_baton): Initialize that flag.
  (conflict_func_interactive): Print a summary of conflicts before starting
    interactive resolution.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1471759 13f79535-47bb-0310-9956-ffa450edef68