Revision 1751509

Improve resolver support for incoming file add vs local file add upon update.

Add the "(R) delete my file and replace it with incoming file" option and
improves the "(i) ignore incoming addition" option, and refine related
option descriptions.

* subversion/libsvn_client/conflicts.c
  (verify_local_state_for_incoming_add_upon_update): New helper function.
   Checks the local WC state for conditions we expect after an update flagged
   an add vs add conflict.
  (resolve_incoming_add_ignore): Use new helper to check conditions before
   marking the conflict resolved.
  (resolve_update_incoming_added_file_replace): New resolution function.
  (configure_option_incoming_add_ignore): Add specific option descriptions
   for the update and switch cases.
  (configure_option_incoming_added_file_replace): Apply option to 'svn update'.

* subversion/svn/conflict-callbacks.c
  (builtin_resolver_options): Tweak "R" short option description to cover
   the update operation case as well as merge.