Bug Fix: Squid may crash, when accessing an SSL certificate with errors

Bug Fix: Squid may crash, when accessing an SSL certificate with errors

This is a security bug.
The bug report is:
   When accessing a revoked certificate (i.e., X509_V_ERR_CERT_REVOKED) Squid
crashes. In ssl/ErrorDetail.cc:223 the detailed message is left blank if the
error is not specifically handled by Squid and the errorpage.cc:1193 assertion
fails while trying to convert the message.

This patch:
 - Handle inside ErrorState::Convert the cases where the ErrorDetail return
   blank error detail string
 - Use a default  detail error message in ssl::ErrorDetail, for the cases
   where the detail error is not defined in TheSslDetailMap.
 - If a name for the ssl::ErrorDetail error code is not defined return the
   numeric error code when the "%err_name" formating code used