top: with new bar graphs, make 'b' toggle unrestricted

top: with new bar graphs, make 'b' toggle unrestricted

While the 'b' toggle remains window based (vs. global)
it should no longer require that the window be visible
and either the 'x' or 'y' toggles to be on. Previously
those requirements were intended to remind a user that
there must be something for this command to highlight.

With the introduction of graph modes (specifically the
the bar graph) the 'bold/reverse' toggle has important
implications beyond highlighting some columns or rows.

The %Cpu(s) graph and Mem portion of the memory graphs
are designed to offer a visual clue as to the separate
elements comprising them. But that separation could be
lost under some X color schemes or when top is running
without color (in monochrome mode) and the block graph
is selected. But, if the graph is then changed to bars
any separation always becomes visible whenever the 'b'
toggle is turned off. Portions then show in 'reverse'.

So from now on we'll check nothing, we'll just toggle.

[ Besides, with all the code thrown at restricting a ]
[ 'b' toggle use, it might have all been for naught. ]
[ That toggle could still be set/unset using the 'Z' ]
[ command and the color mapping screen. Geez Louise! ]

Signed-off-by: Jim Warner <james.warner@comcast.net>