app-layer: protocol change API

app-layer: protocol change API

Add API calls to upgrade to TLS or to request a protocol change
without a specific protocol expectation.

If the HTTP CONNECT session includes a port on the url, use that to
look up the probing parser during protocol detection. Solves a
missed detection of a SSLv2 session that upgrades to TLSv1. SSLv2
relies on the probing parser which is limited to certain ports.

In case of STARTTLS in SMTP and FTP, the port is hardcoded to 443.

A new event APPLAYER_UNEXPECTED_PROTOCOL is set if there was a
mismatch.