Log Message:
Update zeromq to 2.1.11.

0MQ version 2.1.11 (Stable), released on 2011/12/18
===================================================

Bug fixes
---------

* Fixed issue 290, zmq_poll was using system time instead of monotonic
  clock (Mika Fischer).

* Fixed issue 281, crash on heavy socket creation - assertion failure in
  mutex.hpp:91. (Mika Fischer).

* Fixed issue 273, O_CLOEXEC flag used in ip.cpp:192 is supported only
  on Linux kernels 2.6.27+

* Fixed issue 261, assertion failure in kqueue.cpp:76.

* Fixed issue 269, faulty diagnostic code in 2.1.10.

* Fixed issue 254, assertion failure at tcp_socket.cpp:229 on ENOTCONN.

Changes
-------

* Now builds properly on AIX 6.1 (AJ Lewis).

* Builds using libdcekt on HP-UX (AJ Lewis).

* New upstream OpenPGM maintenance release 5.1.118.

* Enabled debugging on assertion failure on Windows (Paul Betts).