- If an untrusted certificate is also found in the list of trusted certificate, issue a warning and skip it, but don't fail.
- Split on -+BEGIN CERTIFICATE-+ instead of "Certificate:" since that's what we're really looking for.
Also fix a long-standing bug: .crl files are not certificates, so we
should not include them when searching for certificates.
Reported by: madpilot, netchild, tijl