glib_socket.h: wrap g_io_channel_*_new() calls portably

The server_socket library (used by the httpd output plugin) didn't
check for WIN32, that's fixed now.

src/event_pipe.c

@@ -21,6 +21,7 @@
 #include "event_pipe.h"
 #include "fd_util.h"
 #include "mpd_error.h"
+#include "glib_socket.h"
 
 #include <stdbool.h>
 #include <assert.h>
@@ -94,11 +95,7 @@ void event_pipe_init(void)
 	if (ret < 0)
 		MPD_ERROR("Couldn't open pipe: %s", strerror(errno));
 
-#ifndef G_OS_WIN32
-	channel = g_io_channel_unix_new(event_pipe[0]);
-#else
-	channel = g_io_channel_win32_new_fd(event_pipe[0]);
-#endif
+	channel = g_io_channel_new_socket(event_pipe[0]);
 	g_io_channel_set_encoding(channel, NULL, NULL);
 	g_io_channel_set_buffered(channel, false);