Documentation follow-up to r25589.
Documentation follow-up to r25589.

* subversion/libsvn_repos/log.c
  (branching_copy_filter): Expound upon concepts in doc string, and
   tweak its formatting.  Tweak wording in inline comment.

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