tools: Fix gpgkey2ssh's most gratuitous errors. Use gpg2, not gpg.
* tools/gpgkey2ssh.c (main): Add support for --help. Replace the most gratuitous asserts with error messages. Invoke gpg2, not gpg.
- Signed-off-by: Neal H. Walfield <neal@g10code.com>
- Debian-bug-id: #380241