_backend_gdk.c on win32

Just trying to build 0.73 on win32 and hot a snag on the new
_backend_gdk. My GTK win32 install, admittedly a bit out of date,
does not have

  #include <gdk/gdkx.h>

I'm using GTK-Development-Environment- and
GTK-Runtime-Environment- which I got a while ago from

Any ideas on how to best proceed?