[MacPorts] #71395: libsigcxx2/3, libxmlxx5: Reduce dependencies

[MacPorts]

#71395: libsigcxx2/3, libxmlxx5: Reduce dependencies
------------------------------------------------+----------------------
  Reporter:  Dave-Allured                       |      Owner:  dbevans
      Type:  enhancement                        |     Status:  assigned
  Priority:  Normal                             |  Milestone:
 Component:  ports                              |    Version:
Resolution:                                     |   Keywords:
      Port:  libsigcxx2, libsigcxx3, libxmlxx5  |
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Old description:

> Dependency `graphviz` can probably be removed for these three ports,
> thereby removing a heavy load.  Upstream changes were made recently,
> making the `dot` command from `graphviz` optional for documentation.
> Upstream discussions and commits:
>
> https://github.com/libsigcplusplus/libsigcplusplus/issues/98
>
> https://github.com/libxmlplusplus/libxmlplusplus/commit/74608b97a3a6a9b230e28c5abaa138160c708838
>
> Because of a parallel dependency chain, reductions will not be realized
> until [https://trac.macports.org/ticket/71389 trac 71389] for `libproxy`
> is completed.

New description:

 Dependency `graphviz` can probably be removed for these three ports,
 thereby removing a heavy load.  Upstream changes were made recently,
 making the `dot` command from `graphviz` optional for documentation.
 Upstream discussions and commits:

 https://github.com/libsigcplusplus/libsigcplusplus/issues/98

 https://github.com/libxmlplusplus/libxmlplusplus/commit/74608b97a3a6a9b230e28c5abaa138160c708838

 Because of a parallel dependency chain, reductions will not be realized
 until #71389 for `libproxy` is completed.

--

Comment (by ryandesign):

 As with any dependency, if the graphviz dependency is removed, steps
 should be taken to ensure that it is not used even if it is installed.

-- 
Ticket URL: <https://trac.macports.org/ticket/71395#comment:1>
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