Issue with ns_color_defined makeIndex argument

[Alex]

I'm currently generalizing some window system-specific code into
terminal hooks, but I've run into an issue regarding ns_color_defined.

In image.c when HAVE_NS is defined, x_defined_color is defined to be:

  ns_defined_color (f, name, color_def, alloc, 0)

But in xfaces.c, defined_color calls ns_defined_color as follows:

  ns_defined_color (f, color_name, color_def, alloc, true);

My intention is to remove defined_color in xfaces.c and the #define
x_defined_color calls in image.c and to replace each call with:

 FRAME_TERMINAL (f)->defined_color_hook (f, color_name, color_def, alloc)

The issue here is that the calls in image.c have makeIndex as 0, and the
calls in xfaces.c as true; is this the intended behaviour?

If so, does anyone have any ideas to rectify this besides adding an
extra argument that non-NS window systems just ignore? I'd rather avoid
doing that.