[BRLTTY] Explicit toggle change

[Stéphane Doyon]

in r7287 you have "Indicate via a tune if an explicit toggle change is 
redundant."

Can you explain the rationale?

With the Alva BC640, Baum, and many others I think, we use separate 
bindings for explicit CSRTRK+on and CSRTRK+off. One reason we have this is 
so we don't have to remember the state. And one convenience is we can 
always use CSRTRK+on to both have the effect of HOME plus ensuring 
tracking is back on. With the new change, if I do CSRTRK+on while tracking 
is already on, I don't get my HOME effect. And I find the new beep really 
strongly conveys that I did something wrong, I find it realyl arresting. 
In short, I don't think I like the change at all :-). But perhaps you had 
a situation where it's beneficial? I suppose the side-effect of going back 
to the cursor on CSRTRK+on means it's not truly a toggle...