TESTING:
- added rapid/traverse movements test
BUGFIX:
- logic error in start_machine_spindle(): asking to stop the spindle
would start it CCW
- typo in invocation of have_gcode_word() when processing M05
BUGFIX:
- home after power on makes no sense, removed for now, moving to the
homing test.
BUGFIX:
- logic error in do_WCS_move_math() was botching polar coordinates.