[RFA/doco] Document the new default for "set print frame-arguments"

[Joel Brobecker <brobecker at adacore dot com>]

This is a slight change of behavior, with a patch posted there:

    http://www.sourceware.org/ml/gdb-patches/2009-03/msg00532.html

Here is the associated documentation update. I added a little reference
to this command in the "Backtrace" node to make it easier to find
this command as well as understanding what the "..." means. And I also
changed the command documentation a bit to reflect the new default.

2009-04-02  Joel Brobecker  <brobecker@adacore.com>

        * gdb.texinfo (Backtrace): Add a parameter in frame 1 of the first
        example, and add a small explanation about it.
        (Print Settings): Change the documentation of the "set print
        frame-arguments" to reflect the fact that the default is now "scalars".

OK to commit?

Thanks,
-- 
Joel