Re: Revise etc/DEBUG documentation

[Davis Herring]

> +It is also useful to have a guaranteed way to return to the debugger
> +at any arbitrary time.  When using X, this is easy: type C-z at the
> +window where you are interacting with GDB, and it will stop Emacs just
> +as it would stop any ordinary program.  When Emacs is displaying on a

I know this is largely old text, but while we're editing it: if GDB was 
attached to a running process ("gdb -p ..."), C-z sent to GDB's terminal 
will just suspend GDB.  With SIGINT set to nostop, you can't stop the 
program from GDB: you have to use its controlling terminal (C-z or C-\, 
since C-c is nostop even thence) if it has one, or else kill(1).

Davis

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