Teredo bubble packets (IPv6 w/ No Next Header and zero Payload Length)
with data extending past the inner IPv6 header (the outer IPv4 header's
Total Length and UDP header's Length indicate this) now only raises
a "Teredo_payload_len_mismatch" weird instead of causing a
ProtocolViolation().
This also fixes a crash in NetSessions::ParseIPPacket() that occurred
when the packet length didn't match the payload length field.
