[rfa] Use get_number_or_range for kill inferior etc.

[Michael Snyder]

Eli Zaretskii wrote:
>> Date: Fri, 25 Feb 2011 14:10:01 -0800
>> From: Michael Snyder <msnyder@vmware.com>
>> CC: "gdb-patches@sourceware.org" <gdb-patches@sourceware.org>
>>
>> 2011-02-25  Michael Snyder  <msnyder@vmware.com>
>>
>> 	* gdb.texinfo (Inferiors and Programs): Update commands to show 
>> 	that they can accept multiple arguments.
> 
> This part is OK, but I still think we should explain the syntax of
> these "lists" in some place, and point to there in each of these
> commands.

I think we all agree on that.