This required for successful linking of libXrender against libNX_X11.

Port from libXfixes commit b031e3b60fa1af9e49449f23d4a84395868be3ab We
need this here to enable linking of current libXrender against
libNX_X11 instead of the system's libX11

The original implementation of this function (libX11 commit
9f5d83706543696fc944c1835a403938c06f2cc5) uses xcb stuff which we do
not have in libNX_X11. So we take a workaround from another lib. This
workaround had been added temporarily to a couple of X extension libs,
see
e.g. https://lists.x.org/archives/xorg-devel/2013-July/036763.html.