Follow-up to r1494966:  When revisions are not given, set them to 0 / HEAD, respectively.  Also, return an empty segment list for empty revision ranges.
Follow-up to r1494966:  When revisions are not given, set them to 0 / HEAD,
respectively.  Also, return an empty segment list for empty revision ranges.

* subversion/libsvn_client/ra.c
  (svn_client__repos_location_segments): revise revision edge case handling

git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@1496886 13f79535-47bb-0310-9956-ffa450edef68

YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion