[doc] Move/edit set/show extended-prompt

[Eli Zaretskii]

> From: Phil Muldoon <pmuldoon@redhat.com>
> Date: Thu, 20 Oct 2011 16:09:13 +0100
> 
> Tom pointed out the set/show extended-prompt section in NEWS was in the
> wrong place.  I moved it, and added a brief summary.  I also fixed two
> typos.
> 
> 
> OK?

Yes, with one change:

> +  Set the GDB prompt, and allow escape sequences to be inserted to
> +  display miscellaneous information (see help set extended-prompt for

Please enclose 'help set extended-prompt' in some kind of quotes.

Thanks.