* configure.ac: Do not build gpg by default.
* gpgsm.c: New options --{enable,disable}-trusted-cert-crl-check.
* certchain.c (gpgsm_validate_chain): Make use of it.
* certchain.c (gpgsm_validate_chain): Check revocations even for
expired certificates.  This is required because on signature
verification an expired key is fine whereas a revoked one is not.
* gpgconf-comp.c: Add gpgsm option disable-trusted-cert-crl-check.