xhc-hb04 remove restriction on step button

Provide hal pins for
  xhc-hb04.stepsize-up (input)
  xhc-hb04.stepsize    (output)

This removes an internal hardwired connection of the step button and
allows a gui to:
 a) display the current increment (xhc-hb04.stepsize).
 b) independently change the increment (typically one would
    'or' the pendant button with a gui button and connect
    to xhc-hb04.stepsize-up

To use the step button with the pendant only, connect it
in the ini file:
 [XHC_HB04_BUTTONS]step = xhc-hb04.stepsize-up
xhc-hb04.cc: create hal pin for sleeping mode

Pendant sends 0x04 0x00 0x00 0x00 0x00 0x00 when it stops updating
display (typically after about 40 seconds of inactivity).  When a
button is pushed, display updates resume.

Detect and update a hal pin named xhc-hb04.sleeping.
In simu_mode, print Sleep delay time and Wake up.