We can end up with / in dependency names from file dependencies but the
deb format doesn't allow this. Filter the names to allow such dependencies
to work. Names have to start with an alphanumeric digit so also handle this.
This allows for future handling of "per file" dependencies similarly to
the rpm backend, bring parity to the functionality of the backends.
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
