Fixed woodhouse example
Problem: breaking change in API

Switching from 'void *' to 'sock_t *' in zpoller, zstr, zmsg, and
zframe broke some upstream applications. (At least czmq++.)

Solution: switch back to using 'void *', and use casts internally
to detect sock_t objects being passed.

At later date we may migrate this using e.g. a macro like CZMQ_SOCK
which the caller can redefine for compatibility.
Problem: it's surprising _print goes to stderr

Fixed in zmsg and zframe, so that _print goes to stdout.
Also clarified what happens to extra message frames in zstr_recvx.
Problem: bind to 9999 failing

Unknown "address already in use" issue caused CZMQ selftest to
fail on development box.

Solution: use ephemeral port number, and make this change in
other classes.
Added tags to various classes

Problem: I want to make methods that accept lots of different types
of object, e.g. to send a zframe, zchunk, zmsg, or string from a
single API call.

Solution: add object detection to target classes. E.g. zmsg_is (m)
Merge pull request #461 from hintjens/master

Fixed  breaking changes to API (sock_t * vs. void *)