fsm: sleep lvp should not be activated at compile time

[0-8-15 User]

The 'USE_SLEEP_LVP' compile time switch should be replaced with a logic that only activates the low voltage protection if any Button-/AUX LEDs are on. It also makes no sense to check the battery voltage four times per minute.

[0-8-15 User (pakutrai)]

I didn't think about the case where the AUX LEDs are used as voltage indicator.

[Selene ToyKeeper (toykeeper)]

I don't really plan to slow down the sleep LVP measurements. There's virtually no benefit to doing so, almost no effect on standby time... and it makes the aux LEDs take longer to respond after the user turns the light off. (voltage tends to recover fairly quickly in the first 10-20 seconds, so I'd like to update the color at least a few times in the first minute)

It could be detected better at compile time though, based on what other flags are active. There may be an argument to be made for not using sleep LVP on devices which don't have enough ROM bytes left for it, but I'm not sure if any of those cases even exist any more.

So this may still be a valid bug, though a minor one.