calc 2.15.1.1 release

[lcn2]

The following are the changes in this release:

Change Makefile.config to, if not using not HomeBrew, then try to
detect macports and/or using /opt/local/{lib,include}.

Put full date range (1989-2025) of calc source into version.h.

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This discussion was created from the release calc 2.15.1.1 release.

[lcn2]

Curious, @pmetzger, if the recent change to Makefile.config make is easier for someone with macports to build calc.