- fix harmless compiler's warnings (unused variables and missed prototype);
- before refusing to delete package because "there are packages installed
that require this package" check that packages in question is actually
installed;
- add new `-r' option to pkg_delete(8), which instructs it to delete not only
packages specified at command line, but all packages that depend on
specified packages as well.
MFC after: 2 weeks
7942a4e1d2