Documenting xaw3d.

[Richard Stallman]

I got a user complaint whose cause is probably that Xaw3d was compiled
with arrows, and he wants the no-arrows behavior.  But he had no way
of knowing this was the cause.  He thought we had made a change in
Emacs.

I think we should add an entry to PROBLEMS about the way to recompile
Xaw3d to control how the scroll bar commands work, so that people
who make complaints like this one will at least have a chance
to find out how they can change the behavior of this.

Can someone who knows the details write an entry?
It would be helpful to show the precise commands to use
to recompile Xaw3d in the two different ways.