Revision 1863290

Merge the r1860936 group from trunk:

 * r1860936, r1860951, r1860958
   Provide a way for svnserve's 'get-deleted-rev' API to return 'not deleted'.
   Justification:
     Error handling was inconsistent across RA layers.
   Votes:
     +1: julianfoad, stsp