Fixes problems with providers that use quite long ECMs/EMMs.

Store message len in int instead of uint8_t to fix transmission of msgs
longer than 255 bytes (size_t was not an option as some functions return
negative values).

Add msg len check to cs378x as it only allows up to 256 bytes data.

Since r10358 oscam expects ECM pid to be send over the camd3 protocol.
This allows ECMs to be retransmitted over gbox.

This change adds support for sending ecm pid.

This patch adds support for connecting to CAMD over IPv6. Nice addition
is that now tsdecrypt tries each of the addresses returned when CAMD
hostname is resolved and connects to the one that works. Resolving
of the server address is done before each connect, which allows for
uninterupted migration of CAMD servers by just changing their DNS
record.

IPv6 functionality can be disabled by using -4/--ipv4 options or
if you fancy only IPv6 servers -6/--ipv6 can be used.

Handle errors in generic camd code instead of protocol code.

This makes do_emm() and do_ecm() take the same parameters. The next
step is to make them take struct camd_msg as single parameter.