D language support

[Mihail Zenkov]

> > +static const char *mangled_str;
> 
> I think this part needs to be rethinked, or at least I don't understand
> why this needs to be a global. Can you elaborate?
> 
> Similarly, I do not understand why ...
> > +/* Temporary obstack used for holding strings.  */
> > +static struct obstack tempbuf;
> ... needs to be a global?

It not real global. As it static it visibility limited to current file. In this case we can 
think about this file as if it was C++ class. IMHO it more easy readable code - we
promptly see all function use same variables.

I see same code in many other places (c-exp.c:3823, c-exp.c:4192, c-exp.c:4609,
ada-lang.c:307, ada-exp.c:2769 and others).

> > +  if (gsymbol->language == language_d
> > +      || gsymbol->language == language_auto)
> > +    {
> > +      demangled =
> > +	d_demangle(mangled, 0);
> 
> Can you join the last two lines?

Current code:

  if (gsymbol->language == language_objc
      || gsymbol->language == language_auto)
    {
      demangled =
        objc_demangle (mangled, 0);
      if (demangled != NULL)
        {
          gsymbol->language = language_objc;
          return demangled;
        }
    }
  if (gsymbol->language == language_cplus
      || gsymbol->language == language_auto)
    {
      demangled =
        cplus_demangle (mangled, DMGL_PARAMS | DMGL_ANSI | DMGL_VERBOSE);
      if (demangled != NULL)
        {
          gsymbol->language = language_cplus;
          return demangled;
        }
    }
  if (gsymbol->language == language_java)
    {
      demangled =
        cplus_demangle (mangled,
                        DMGL_PARAMS | DMGL_ANSI | DMGL_JAVA);

Still i should join it?