[doc] Mention accelerated watchpoint conditions in the gdb manual

[Eli Zaretskii]

> From: Thiago Jung Bauermann <bauerman@br.ibm.com>
> Date: Tue, 17 Aug 2010 16:40:39 -0300
> 
> I mentioned this feature in the NEWS file but I just realized that it
> would be useful to mention in the manual too. Ok to apply? For the
> branch too?

Yes and yes.  Thanks.

> +@smallexample
> +(@value{GDBP}) watch @var{ADDRESS|VARIABLE} if  @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
> +@end smallexample

Please break the long line in two: it's too long and will overflow the
page boundary in the printed manual.

Also, please add a "@cindex DVC register" entry here.