[Cygwin] Fix for: detaching crashes the inferior.

[Eli Zaretskii]

> Date: Mon, 09 Apr 2007 03:06:20 +0100
> From: Pedro Alves <pedro_alves@portugalmail.pt>
> 
> Is there a case where we can get to to_detach
> without remove_breakpoints being called?  I don't think there
> is - we always get here through normal_stop, right?

If you think this must be so, but are unsure, you can add a flag that
is turned off in remove_breakpoints and turned on when a breakpoint is
set.  Then, in to_detach, if the flag is on, you can scream bloody
murder (and even abort(), if you think it's fatal).  Once users start
using the modified version, you will soon know whether the assumption
was wrong...