Fix an ancient bug which caused mod_dav_svn to a) transmit some opaque URLs with double slashes, and b) send baseline collection urls that were altogether mis-rooted:
Fix an ancient bug which caused mod_dav_svn to a) transmit some opaque
URLs with double slashes, and b) send baseline collection urls that
were altogether mis-rooted:

   ...
   <S:add-directory name="G" bc-url="/A/D/G">
   <D:checked-in>
   <D:href>/svn-test-work/local_tmp/repos/!svn/ver/1//A/D/G</D:href>
   </D:checked-in>
   ...

* subversion/mod_dav_svn/reports/update.c
  (get_from_path_map): Use svn_path_join() instead of apr_pstrcat()
    because the former understands path semantics.

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion