Kill the pre-version 3 intro protocol code with fire.

We still have code for dealing with version 0, 1, and 2 of the HS intro protocol.

From rend-spec.txt:

As of Tor 0.2.0.7-alpha and 0.1.2.18, clients switched to using the v2 intro format.

From the release notes:

Bugfix on 0.2.1.6-alpha, when the v3 intro-point protocol (the first one which sent a timestamp field in the INTRODUCE2 cell) was introduced;

Anything that generates INTRODUCE cells with these versions are long dead, so the code for handling this protocol version should be removed.