- Add to the wrapper generator (add_method) the release_GIL_and_enable_signal option which :
- release the GIL
- save the python signal handler
- enable the C++ triqs signal handler instead.
- undo all of this after the code runs, or in a case of exception.
- used python include, ceval.h, line 72 comments and below.
- reworked the triqs::signal_handler.
simple C like function, no object (no need).
start, stop, received, cf header file.
- clean the call_back.cpp : only place using the signal directly
(qmc uses the callback).
in particular, remove the old BOOST CHRONO, since
the std::chrono works fine on platforms we use now.
