c reactor / gordon's examples

Hi Everyone,

I've been doing some work on a C reactor API for proton that is intended to
fit both alongside and underneath what gordon has been doing in pure
python. I have several goals with this work.

- Simplify/enable a reactive style of programming in C that is similar to
what gordon has built out in pure python.

- Provide a C API that translates well into the python/ruby/etc bindings,
so that sophisticated handlers can be written once in C rather than being
duplicated in each scripting language.

- Preserve the extensibility/flexibility that comes with being able to
define custom handlers in the bindings, so python/ruby/etc handlers can
intermix well with C handlers.

- Provide a C API that translates well into javascript via emscripten. In
some ways this is similar to the above goals with the other language
bindings, however I mention it separately because there are additional
memory management constraints for javascript since it has no finalizers.

I believe I've made significant progress towards most of these goals,
although there is still plenty of work left to do. I'd like to share a few
examples both to illustrate where I am with this and to solicit feedback
and/or help.

Let me say up front that these examples aren't intended to be "hello world"
type examples. The focus of this work has really been on the
reactor/handler/event-dispatch infrastructure, and so the example I've
chosen is really intended to illustrate key aspects of how this works. To
do that I've built an example that sets up a recurring task, a server, and
a client, all within the same process and then sends a number of messages
to itself.

I've included the same example twice, once written in C and once written in
the python binding of the C API. Please have a look and let me know what
you think.

--Rafael