[m-rev.] for review: fix an XXX: escape characters returned by deconstruct.functor/4

[Zoltan Somogyi]

On Fri, 8 Jun 2018 10:05:19 -0400 (EDT), Julien Fischer <jfischer at opturion.com> wrote:
> Fix an XXX: escape characters returned by deconstruct.functor/4.
> 
> runtime/mercury_ml_expand_body.h:
>      Fix an XXX: escape characters in functors.

The output of the deconstruct_arg.m test case still contains unescaped
characters. This is because we print the value of the whole term under test
using io.print, which calls stream.string_writer.print, which calls the put
method, which calls write_char. No predicate in that chain quotes the char.

It seems to me that if deconstruct.functor quotes these special chars, then
stream.string_writer.print should too. And changes to both should be mentioned
in the NEWS file, since they are user-visible changes in behavior.

Zoltan.