Add note about initializing submodules.
Minimal rewrite of poller.c in C++
poller.cpp: use modern libevent API for evsignal
common/poller.cpp: simplify IghtEvent implementation
common/poller.cpp: remove unused headers
Get rid of ight_wrappers.h

Move the poller-related prototypes in poller.h and get rid
of ight_wrappers.h, which now contains nothing.

This is functional to the C++-ification of the Poller, because
the Poller C++ class will be added to common/poller.h.
net/protocol.h: remove unused typedef
poller: use better accessor names
Convert poller to use std::function()
Rewrite the poller using C++
configure.ac: check whether C++ lib supports C++11

We've started to use many C++11 features with the new Poller, e.g.,
std::function and std::move, so better be sure that we are on a system
with a C++11 compliant standard library.

While there, improve the error case of the check whether the
C++ compiler knows the C++11.
configure.ac: force libc++ on MacOS 10.8

Otherwise, I need to manually edit Makefile each time to
compile libight on my MacOS system.
Plug memory leak in IghtDelayedCall
IghtPoller(): use more appropriate exception

Distinguish between bad_alloc, used when malloc() fails, and
runtime_error, raised when something unexpected happens.
Add nonset function test case to .../delayed_call.cpp

Make sure that, if the caller passes us a std::function object
that is not bound to any function, nothing happens.
delayed_call.cpp: Add commented out non compiling test case

I want to verify that one cannot make copies of IghtDelayedCall,
but I don't know how to do that, since the commented out code should
not compile exactly because copies are forbidden.

Maybe a script that tries to compile and fails on success, succeeds
on error (as expected)?
poller.cpp: fix typo
Poller(): throw better exception if event_add() fails
Drop more comments in test/.../delayed_call.cpp
test/.../delayed_call.cpp: test IghtDelayedCall life cycle

Add a test case that shows that it is safe to store the delayed
call inside an object, such that, when/if the object is destroyed,
the delayed call is also unscheduled and destroyed.