[MacPorts] #43704: unify the use of +threads as a variant name

[MacPorts]

#43704: unify the use of +threads as a variant name
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  Reporter:  mojca@…                             |      Owner:  macports-
      Type:  enhancement                         |  tickets@…
  Priority:  Normal                              |     Status:  new
 Component:  ports                               |  Milestone:
Resolution:                                      |    Version:
      Port:  boost cherokee gauche hdf5 hdf5-18  |   Keywords:
  raxml                                          |
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Comment (by mmoll@…):

 Thread safety is different from multi-threaded. Thread-safe code can be
 used in multi-threaded code, but isn't necessarily multi-threaded itself.
 Multi-threaded code necessarily must be thread-safe. Nevertheless, I can
 see the value in having fewer variant names. It'd be nice if a multi-
 threaded port that depended on hdf-18 would build the threadsafe variant
 of hdf5-18. That is more likely to happen if the hdf5-18 variant is named
 "threads". In other words, I'd be okay with this change, as long as the
 variant description is clear what it means in each case.

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Ticket URL: <https://trac.macports.org/ticket/43704#comment:3>
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