if a port needs 2.x then set MODPY_VERSION=${MODPY_DEFAULT_VERSION_2}.
This commit doesn't change any versions currently used; it may be that
some ports have MODPY_DEFAULT_VERSION_2 but don't require it, those
should be cleaned up in the course of updating ports where possible.
Python module ports providing py3-* packages should still use
FLAVOR=python3 so that we don't have a mixture of dependencies some
using ${MODPY_FLAVOR} and others not.
GNU Units converts quantities expressed in various systems of
measurement to their equivalents in other systems of measurement. Like
many similar programs, it can handle multiplicative scale changes. It
can also handle nonlinear conversions such as Fahrenheit to Celsius
or wire gauge, and it can convert from and to sums of units, such as
converting between meters and feet plus inches.
