Robot: remove unused variable
USB DFU: keep usb connected while we respond to reset request.

we also become a kernel module so we can receive the on idle event. This would be an ideal place to do shutdown tasks, eg save position somewhere
Extruder: make sure we have a block to release, avoid segfaults
utils: is_alpha, is_digit, is_numeric, is_alphanum, is_whitespace utility functions
Gcode: get_int method to shortcut string->float->int conversion
SlowTicker: implement G4 pause