Improve the doc. string for svn_opt_parse_revision.
Improve the doc. string for svn_opt_parse_revision.

* subversion/include/svn_opt.h
  (svn_opt_parse_revision): Don't say that it yields numeric revisions,
    because it can yield symbolic ones too.  Mention that the date form is
    accepted as well as plain symbolic revision specifiers.  State the use
    of the 'pool' argument.


git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@851890 13f79535-47bb-0310-9956-ffa450edef68

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