Peek and Splice: SNI to external_acl

Peek and Splice: SNI to external_acl

Support the %ssl::>sni formating code with external_acl helpers and
access logging. The new code prints the SNI name sent by the SSL client.
If no SNI information is available, the code expands into a dash. It is
currently supported only after the peek, stare, or splice SSL bumping
actions. Note that older clients (e.g., IE on Windows XP) do not send SNI.

This is a Measurement Factory project