Chain glib's SIGCHLD handler from Emacs's (Bug#14474).

Chain glib's SIGCHLD handler from Emacs's (Bug#14474).

* process.c (dummy_handler): New function.
(lib_child_handler): New static var.
(handle_child_signal): Invoke it.
(catch_child_signal): If a library has set up a signal handler,
save it into lib_child_handler.
(init_process_emacs): If using glib and not on Windows, tickle glib's
child-handling code so that it initializes its private SIGCHLD handler.
* syssignal.h (SA_SIGINFO): Default to 0.
* xterm.c (x_term_init): Remove D-bus hack that I installed on May
31; it should no longer be needed now.