* tests/gpgscm/ffi.c (do_get_time): New function.
(ffi_init): Expose new function.
* tests/gpgscm/ffi.scm (get-time): Document new function.
* tests/gpgscm/time.scm: New file.
* tests/openpgp/quick-key-manipulation.scm: Use the new facilities to
check the expiration times of created keys.
* tests/openpgp/tofu.scm: Use the new module.