Fix up some doc strings and consolidate two similar functions into one.
Fix up some doc strings and consolidate two similar functions into one.

See http://svn.haxx.se/dev/archive-2011-11/0301.shtml

* subversion/libsvn_client/merge.c
  (get_most_inclusive_start_rev,
   get_most_inclusive_end_rev): Remove both of these and replace with...

  (get_most_inclusive_rev): ...this.  Note that the logic in
   get_most_inclusive_start_rev which checked for "dummy" ranges was
   removed in the new combined function; this logic has been unnecessary
   since r872890.

  (do_directory_merge): Replace calls to get_most_inclusive_*_rev with
   get_most_inclusive_rev.  Correct a in-line comment before one of those
   calls.


git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@1204617 13f79535-47bb-0310-9956-ffa450edef68

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