[WIP] substitute pkgng for pkg_info

"__pkgng__" is the new package manager.
  see http://www.freebsd.org/doc/en/books/handbook/pkgng-intro.html

I suppose it should use __pkgng__ instead of `pkg_info`, `pkg_add`, and such.
__pkgng__ supports FreeBSD 9.1 over, and moreover, `pkg_info` and such have
been removed since FreeBSD 10.0-CURRENT.