[PATCH 2/2] Add "set/show debug unwinder" prefix commands.

[Eli Zaretskii]

> From: Samuel Bronson <naesten@gmail.com>
> Cc: Samuel Bronson <naesten@gmail.com>
> Date: Fri, 29 May 2009 19:16:27 -0400
> 
> Also add one subcommand for tracing the sniffing of stack frames by
> unwinders.

Thanks.

If the code is accepted, we will need a suitable change for the manual
describing this new command.