Command: ./release-tool i18n lupdate

Signed-off-by: Konrad Gräfe <kgraefe@paktolos.net>

This change adds testing all KeeAgentSettings fields including their XML
conversions by separately:
- verifying the default value,
- change the current to something else,
- convert the KeeAgentSettings object to XML,
- convert it back to a second KeeAgentSettings object,
- compare both objects to be equal and
- verify that the new value landed in the field of the second
  KeeAgentSettings object.

Signed-off-by: Konrad Gräfe <kgraefe@paktolos.net>

This change implements loading ssh-agent destination constraints from
KeeAgent.settings into the ssh-agent. For now there is no UI so
configuration must be done in KeePass2/KeeAgent.

The ssh-agent constrain extension is described at [1]. However, I found
it partly misleading:
- in the constaint array each constraint is enveloped where in the
  keyspec arrays the keyspec are just appended to the constraint.
- each constraint and host has an additional string field reserved for
  future use.
The actual structure has been obtained from openssh ssh-add source code [2].

[1]: https://www.openssh.com/agent-restrict.html
[2]: https://github.com/openssh/openssh-portable/blob/3ad669f81aabbd2ba9fbd472903f680f598e1e99/authfd.c#L538

Signed-off-by: Konrad Gräfe <kgraefe@paktolos.net>

Signed-off-by: Konrad Gräfe <kgraefe@paktolos.net>

Signed-off-by: Konrad Gräfe <kgraefe@paktolos.net>

Signed-off-by: Konrad Gräfe <kgraefe@paktolos.net>