Modify IOSource Manager to implement new loop architecture

- Removes entire FindSoonest method that includes all of the calls to select() for checking for ready sources
- Removes FD_Set checking against IOSources
- Adds system for registering and unregistering file descriptors from IOSources. This allows individual sources to mark themselves as ready to be checked by the loop as they become available.
- Adds entirely new loop architecture based on checking the IOSources for when their next timeout is, and then waiting for either that timeout or when the next source is ready. This also implements the polling based on what the OS supports, instead of just calling select() on all platforms. Currently it supports kqueue, epoll, and plain poll.
- Adds system for pinging the loop to force it to wake up

src/main.cc

@@ -256,6 +256,8 @@ void terminate_bro()
 
 	terminating = true;
 
+	iosource_mgr->Wakeup("terminate_bro");
+
 	// File analysis termination may produce events, so do it early on in
 	// the termination process.
 	file_mgr->Terminate();
@@ -332,6 +334,9 @@ RETSIGTYPE sig_handler(int signo)
 	set_processing_status("TERMINATING", "sig_handler");
 	signal_val = signo;
 
+	if ( ! terminating )
+		iosource_mgr->Wakeup("sig_handler");
+
 	return RETSIGVAL;
 	}
 
@@ -662,6 +667,7 @@ int main(int argc, char** argv)
 	if ( reporter->Errors() > 0 )
 		exit(1);
 
+	iosource_mgr->InitPostScript();
 	plugin_mgr->InitPostScript();
 	zeekygen_mgr->InitPostScript();
 	broker_mgr->InitPostScript();
@@ -878,11 +884,6 @@ int main(int argc, char** argv)
 
 	have_pending_timers = ! reading_traces && timer_mgr->Size() > 0;
 
-	iosource_mgr->Register(thread_mgr, true);
-
-	if ( zeek::supervisor_mgr )
-		iosource_mgr->Register(zeek::supervisor_mgr);
-
 	if ( iosource_mgr->Size() > 0 ||
 	     have_pending_timers ||
 	     BifConst::exit_only_after_terminate )