main: Add Windows Service support

I've added PIPE_EVENT_SHUTDOWN because calling g_main_loop_quit() do not work when called from another thread.
Main thread was sleeping in g_poll() so I needed some way to wake it up.

By some strange reason call close(event_pipe[0]) in event_pipe_deinit() hangs.
In current implementation that code never reached so that was not a problem :-)
I've added a conditional to leave event_pipe[0] open on Win32.

src/event_pipe.c

@@ -116,7 +116,10 @@ void event_pipe_deinit(void)
 	g_source_remove(event_pipe_source_id);
 	g_io_channel_unref(event_channel);
 
+#ifndef WIN32
+	/* By some strange reason this call hangs on Win32 */
 	close(event_pipe[0]);
+#endif
 	close(event_pipe[1]);
 }