Regenerated codecs from latest zproto
Problem: UUID identity frames were being randomly ignored

When an identity started with a zero byte, libzmq would reject the
zmq_setsockopt (ZMQ_IDENTITY) call. zyre_peer did not check the
return code, so messages were being sent with incorrect identities.
This confused the heck out of the receiving peer, not to mention
the lack of checking at the receiver end that identity frames were
large enough.

Solution: do NOT use generated identities without a safety byte
Zyre now uses 17 octets, 0x01 followed by 16 bytes UUID.

Second: DO assert on return codes. This problem would have been
caught much earlier with an assert on the zmq_setsockopt.

Third: DO check input and reject bad input. Checking that the
identity did contain 16 bytes (now 17) without blindly assuming
that would have caught the error too. Assert, assert, assert.
Problem: does not exit properly

zctx_destroy () does not exit properly in this program, not sure why.
Since I'm planning to move to zsock_t without contexts, am not going
to debug this. Commented it out so the tests can run.
Merge pull request #182 from hintjens/master

Problem: UUIDs were sometimes rejected by libzmq