On the 'move-tracking-2' branch: Tweaks to 'svnmover'.

* subversion/libsvn_delta/compat3.c
  (branch_map_get_eid_by_path): Don't crash if the mapping is incomplete for
    some path other the one we're looking up.

* subversion/svnmover/svnmover.c
  (find_el_rev_by_rrpath_rev): Take the revision as a plain number.
  (execute): Resolve revision specifiers to a number here, and support the
    'head' keyword.


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/move-tracking-2@1636593 13f79535-47bb-0310-9956-ffa450edef68