Merge pull request #562 from hintjens/master

Problem: creating sockets still needs multiple calls
zsys.c: Fix function zsys_vprintf for mingw compilers
zbeacon.c: Fix function s_get_interface for mingw compilers
Merge pull request #564 from guidefloripa/master

Fix mingw compilation
Eliminate forcin pointers/integers to bool, fix errno redefine.
Cosmetic
Remove crypt32.lib from libsodium VS import dependencies.
Merge pull request #565 from evoskuil/master

Fix errno redefinition
Create a monotonic clock function, use it where time offsets are computed.

Problem:  If the system time is set backwards while a czmq application is
          running that has timers set on a zloop, those timers will stop
          until the system time reaches its previous value.

Solution: Introduce a monotonic clock that is not affected by system time
          changes.  Use this clock where time offsets are computed.
Merge pull request #566 from mtspencer/master

Create a monotonic clock function, use where time offsets are computed
Problem: need UUID construction from string

Solution: add zuuid_set_method.
Problem: not working properly on ZeroMQ/2.x any more

The problems are mainly with inproc bind/connect. In 2.x these have
to come in the right order, and with multiple threads, we need a
short pause before connect is safe to go.

I might fix this in zsock_connect by pause/looping a few times, if
we're on 2.x and the connect fails.