Merge from vendor branch PKGSRC:

Merge from vendor branch PKGSRC:
Import pkg_install-20090424:
Make pkg_delete -d the default behavior, remove the option.
Remove pkg_create -R support (reorder @dirrm entries).
Introduce new plist command @pkgdir, which makes pkg_add add
this directory if it doesn't exist already and pkg_delete remove it
only if no other package has a @pkgdir entry for it. Otherwise
directories are pruned when the last file or directory in them is
removed. @dirrm is now a pure hint, if the directory doesn't exist, it
will be silently skipped.