ZMQ_PROBE_ROUTER was defined as read-only

- made read/write so the option can be set
- also updated all man pages
ZMQ_PROBE_ROUTER isn't readable via libzmq API
Merge pull request #331 from hintjens/master

ZMQ_PROBE_ROUTER was defined as read-only
Rationalized _print/_fprint method names

- library used a mix of _dump and _print
- now _print consistently sends to stdout
- _fprint consistently present, accepting FILE *
- _dump reimplemented as deprecated macros
Merge pull request #332 from hintjens/master

Rationalized _print/_fprint method names
Merge remote-tracking branch 'upstream/master'
implemented zproxy_pause and zproxy_resume