Fix compiling on windows/mingw with automake build system.

Bug: https://bugs.freedesktop.org/show_bug.cgi?id=95191
Reviewed-by: Simon McVittie <simon.mcvittie@collabora.co.uk>

dbus/dbus-sysdeps-thread-win.c

@@ -28,6 +28,8 @@
 #include "dbus-threads.h"
 #include "dbus-list.h"
 
+#include <stdio.h>
+
 #include <windows.h>
 
 static dbus_bool_t global_init_done = FALSE;