This function will verify the peers certificate and store
the status in the status variable as a bitwise ord gnutls_certificate_status_t
values or zero if the certificate is trusted. Note that value in status is set only when the return value of this function is success (i.e, failure
to trust a certificate does not imply a negative return value).
The default verification flags used by this function can be overridden
This function will take into account the OCSP Certificate Status TLS extension,
as well as the following X.509 certificate extensions: Name Constraints,
Key Usage, and Basic Constraints (pathlen).
To avoid denial of service attacks some
default upper limits regarding the certificate key size and chain
size are set. To override them use gnutls_certificate_set_verify_limits().
Note that you must also check the peers name in order to check if
the verified certificate belongs to the actual peer, see gnutls_x509_crt_check_hostname(),
or use gnutls_certificate_verify_peers3().