tests: Add another check to gpg/t-verify.
* tests/gpg/t-verify.c (PGM): New. Use it instead of __FILE__. (test_sig1_plus_unknown_key): New test signature. (check_result): Allow checking of several signatures. (main): Check a signature with a know and an unknown key.
- Signed-off-by: Werner Koch <wk@gnupg.org>