Stop the framework within signal handler.

[PengZheng]

Currently celix_framework_stopBundle is called in signal handler of SIGINT and SIGTERM to stop the framework.
This function calls bunch of unsafe functions, and thus is not async-signal-safe. See man signal-safety for more information.

celix/libs/framework/src/celix_launcher.c

Lines 104 to 122 in 62480b1

	struct sigaction sigact;
	memset(&sigact, 0, sizeof(sigact));
	sigact.sa_handler = shutdown_framework;
	sigaction(SIGINT, &sigact, NULL);
	sigaction(SIGTERM, &sigact, NULL);
	memset(&sigact, 0, sizeof(sigact));
	sigact.sa_handler = ignore;
	sigaction(SIGUSR1, &sigact, NULL);
	sigaction(SIGUSR2, &sigact, NULL);
	int rc = celixLauncher_launchWithConfigAndProps(config_file, &framework, packedConfig);
	if (rc == 0) {
	g_fw = framework;
	celixLauncher_waitForShutdown(framework);
	celixLauncher_destroy(framework);
	}
	return rc;

We need a reliable mechanism to communicate with the Celix event loop from within a signal handler.

[PengZheng]

Duplicate of #215