bdring/FluidNC TestPullups

on GitHub

This is a test release for a bug that only affects active-high limit pins with large-value/weak pulldowns. The problem is that the internal pullup resistor on limit pins was activated even if you did not say :pu in the config file. If there is a weak pulldown, the combination of the pullup and the weak pulldown can make the pin float at an intermediate voltage which could be interpreted as high even if the external switch is not active, so there would never be a low-to-high transition.