* subversion/libsvn_client/mergeinfo.h,
  subversion/libsvn_client/mergeinfo.c
  (svn_client__record_wc_mergeinfo_catalog): Add more documentation.

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1452583 13f79535-47bb-0310-9956-ffa450edef68