bug#21777: 25.0.50; gud-gdb uses a pager, which is harmful inside emacs

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: dima@secretsauce.net,  21777@debbugs.gnu.org,  schwab@linux-m68k.org
> Date: Thu, 24 Sep 2020 16:15:29 +0200
> 
> Anyway, set-process-window-size is indeed called in M-x gud-gdb
> buffers.  So does M-x gdb buffers...  but in that case, gdb just seems
> to ignore it, as it should.  So M-x gdb sets up gdb in a way that
> gud-gdb doesn't.

Yes, "M-x gdb" doesn't start Readline in GDB, and so GDB doesn't think
it runs with output to a terminal device.  "M-x gud-gdb", OTOH,
invokes GDB as an interactive program via PTY.