This reverts commit 82c485e5.

...and merge in Z:ZMap::Core.

In preparation for Zircon::Protocol::JSON.

Tk not required!

This will allow creation of Z:Context::ZMQ::AnyEvent.

...which will force AnyEvent to erroneously use Tk stuff.

Z:TkZMQ::Context: disconnect Tk fileevent during receive callback, to prevent inadvertent nested events.

with the understanding that close(FH)
  is documented to return a failure without die()ing,
  but when STDERR is tied there can be an exception

for RT#407413 <- RT#292118
as in e-o 77a2556d4bfeddbd3a55cecfa0285cc4b680c651

with the understanding that close(FH)
  is documented to return a failure without die()ing,
  but when STDERR is tied there can be an exception

for RT#407413 <- RT#292118
as in e-o 77a2556d4bfeddbd3a55cecfa0285cc4b680c651

One context per session in the ZeroMQ world.