Initial import of genpkgng, a utility which will convert a pkgsrc
binary package to a FreeBSD binary pkg.  pkgsrc binary packages keep
more metadata, and do Dewey matching on package version numbers, so
it's not possible to convert in the other direction.

The DESCR says:

	This is a small utility to generate a FreeBSD pkg binary package
	from a pkgsrc binary package. It is invoked simply, using a
	command like:

		genpkgng ssam-1.9nb1.tgz

	and it will convert the pkgsrc binary package to a pkg one:

		% ./genpkgng.sh perl-5.18.1nb2.tgz
		Converting perl-5.18.1nb2.tgz
		-rw-r--r--  1 agc  users  16597860 Apr 24 19:01 perl-5.18.1nb2.txz
		%