Allow level parameter in frame

[oriolarcas]

GDB frame command can simultaneously select the stack level and display the frame.

This patch does the same:

define frame
    if $argc == 1
        select-frame $arg0
    end
    info frame
    info args
    info locals
end
document frame
Syntax: frame <LEVEL>
| Print current stack frame, or the LEVEL stack frame.
end

[ObiWahn]

Selecting frames via f / frame #num does not work please do not replace build in commands.

[oriolarcas]

Since this is what gdbinit does already, this patch fixes this problem.

[ObiWahn]

So with your patch:

f 6
l

should work?

[oriolarcas]

Yes, "f [frame number]" works with this patch.