[RFC] Change "set print frame-arguments"'s default to scalars

[Joel Brobecker]

>         Change the default value for "set print frame-arguments" to scalars.
>         * stack.c (print_frame_arguments): Set initial value to "scalars".

Given the positive reaction to this change, I checked it in, together
with Tom's testsuite updates (Thank You!)

I'll look at the documentation now, in case an update might be useful.

-- 
Joel