RFA: doc: update 'dump' documentation

[Eli Zaretskii]

> From: Jim Blandy <jimb@redhat.com>
> Date: 07 May 2003 15:16:05 -0500
> 
> gdb/doc/ChangeLog:
> 2003-05-07  Jim Blandy  <jimb@redhat.com>
> 
> 	* gdb.texinfo (Dump/Restore Files): Update documentation for
> 	'dump', 'append', and 'restore': note that format argument is
> 	optional; simplify presentation of the command variants; and be
> 	more precise about the formats.

Approved.  Thanks.