devel/R-cran-clock: Add new port

Provides a comprehensive library for date-time manipulations using
a new family of orthogonal date-time classes (durations, time points,
zoned-times, and calendars) that partition responsibilities so that
the complexities of time zones are only considered when they are
really needed. Capabilities include: date-time parsing, formatting,
arithmetic, extraction and updating of components, and rounding.