Log Message:
Update package Makefile now that bsd.pkg.extract.mk is using the
"extract" script for extraction.  Many cases where a custom EXTRACT_CMD
simply copied the distfile into the work directory are no longer
needed.  The extract script also hides differences between pax and
tar behind a common command-line interface, so we no longer need code
that's conditional on whether EXTRACT_USING is tar or pax.