Allow aborting macros Including homing moves - "not quite an emergency, but STOP"

[T3P3]

Allow cancellation of the following:

• running system macro like bed probing, homing etc.
• wait for temp
• running user macro
  These need to be able to be cancelled from the same input as they came from.
  It is accepted that this could leave the machine in an unknown state, so for example, cancelling homing would leave the axes that were marked as unhomed at the start of the homing macro, unhomed.

would this supersede M108?

Ideally these work arounds could be replaced by a gcode that cancelled the wait/macro.

Consideration should be made for what happens after the cancel, my initial thoughts:

• If a job is processing/pausing/paused then it should be cancelled.
• heating - leave temperatures set but stop waiting
• bed probing - do not set the Z 0 point or save a height map if its meshing.
• user macros - equivalent to a break

There is a work around which replaces M116 with a while loop and check if a global variable changes state in order to cancel the wait for temp however it requires the cancel to com from a different input channel from where the wait was called. (This work around is also possible to use to cancel out of bed probing)

[T3P3]

Also this should allow running conditional gcode to be cancelled.

[dc42]

It should already be possible to cancel M116 waits using M108, although the documentation for M108 doesn't mention it. I will update the documentation.

[T3P3]

Aborting a homing move is effectively a "not quite an emergency" stop.

Cancelling M116 heating wait is M108 - check this works correctly

Aborting macros, whatever a macro is addressing is now an unknown state.