gmmproc: Added parameter exception_handler in _WRAP_VFUNC (bgo#735132)

This change allows developer to use custom exception handler, instead of
using Glib::exception_handlers_invoke() method. It might be useful, if
developer can't get access to a thread, where exception might appear, or
it is very difficult to register handler in this thread.

     * tools/m4/signal.m4:
	* tools/m4/vfunc.m4:
	* tools/pm/Output.pm:
	* tools/pm/WrapParser.pm: added additional parameter
	  to a _WRAP_VFUNC and _WRAP_SIGNAL, allowing write custom
          exception handlers