Only use SSL_AD_* internally.

Only use SSL_AD_* internally.

Due to hysterical raisins there are three different types of defines for
alerts. SSL3_AD_* are from SSLv3, TLS1_AD_* are from TLSv1.0 onwards and
SSL_AD_* currently map to either an SSL3_AD_* or TLS1_AD_* define.

Currently, all three of these are used in various places - switch to using
just SSL_AD_* values internally, as a first step in cleaning this up.

ok tb@