bug#2136: cleanup: Fresume_tty and Fsuspend_tty

[Dan Nicolaescu <dann@ics.uci.edu>]

Eli Zaretskii <eliz@gnu.org> writes:

  > > Date: Sat, 31 Jan 2009 13:22:16 -0800 (PST)
  > > From: Dan Nicolaescu <dann@ics.uci.edu>
  > > Cc: 2136@emacsbugs.donarmstrong.com
  > > 
  > > Can you have multiple ttys in MSDOS?
  > 
  > No, of course not.  Not if by ``tty'' you mean an interactive
  > terminal.
  > 
  > > Otherwise suspend-frame won't call supend-tty.
  > 
  > It can be tricked into doing that, since the test in controlling-tty-p
  > is very naive.

Then the test needs to be improved...

  > >   >  For resume-tty, I just invoked it directly.
  > > 
  > > See above, this function only makes sens when using multiple ttys. 
  > 
  > If you mean the full functionality, then yes, I agree.  However, since
  > the current uses of these two functions are so few, I cannot yet say
  > that having them not fboundp will or won't do harm for the DOS port.
  > For now, they are more or less no-ops, which certainly doesn't do any
  > harm, at least AFAICS.

It complicates the code, I just recently fixed in bug there, that's how
I run into this.

  > On the other hand, keeping them out of the DOS build would mean the
  > same #ifdef's will have to stay, just in different places, which won't
  > make the sources more clean, IMO.

Given that the functions are no-ops for DOS, just to put an #ifndef
inside the body and make them just return Qnil, that way it's pretty
clear they  are no-ops.