remove trivial functions like servo, adc
remove trivial functions like servo, adc

They are developed on separate branches.

In fact there is one critical issue comes from Servo lib:
Servo::attach() enables a timer, it may affect many other
unrelated functions, such as SPIFFS.exist?
So remove it on master branch decidedly...

linkgo/neurite,linkgo/neurite,linkgo/neurite,linkgo/neurite