[PATCH] Tying validation errors to certificates

When Squid sends errors to the certificate validation daemon, the daemon
cannot tell which certificate caused which error. This is especially bad
because the validator has to return that same information in the
response (the response format requires the validator to match the error
to the certificate).
This patch adjust the validation request format to provide that
information using a set of the following key=value pairs:

    error_name_N=the name of the certificate error number N
    error_cert_N=the ID of the certificate which caused error_name_N

where N is non-negative integer. N values start from zero and increase
sequentially.

This is a Measurement Factory project