Addressing issue #2767

If Marlin is blocking the serial input or command queue for any length
of time (for example more than 2 seconds), it needs to send a message
to serial out to inform the host that it is busy. Marlin should only
send these messages out when busy, and preferably not when trying to
print formatted output.

diagonal_rod hadn't been used anywhere.

rebased
corrected spelling
changed to #elif for error

Still with MIN_Z_HEIGHT_FOR_HOMING but con be done with (folder wide) search-replace when we have a better name.

Add 'ok' output for G29 actually closing the file.
Handle M110 when received without linenumber/checksumm.

Addressing issue #2767

Apply `constrain`, `NOMORE`, `NOLESS` and `CRITICAL_SECTION` macros
wherever possible.

Based on #2860 - rebased for RCBugFix

Add watchdog reset in the kill loop to simplify recovering.

twice for a servo based probe.

raise_z_after_probing() was only called if the printer type was set to a
DELTA or if the printer had a docking sled for the probe.

Refresh previous_cmd_ms during run_z_probe() to prevent:
stepper shutdown for expired DEFAULT_STEPPER_DEACTIVE_TIME
and extrudes for expired EXTRUDER_RUNOUT_SECONDS
(https://github.com/MarlinFirmware/MarlinDev/issues/238)

In the wait loops of M109 M190 idle() is called, what checks
stepper_inactive_time against previous_cmd_ms.
Because we can be several minutes inside the loop, resetting
previous_cmd_ms only outside the loop caused stepper shutdowns.

The name of previous_cmd_ms does not really reflect its use. It's set
not only when a new command was received or executed but also in many of
the movement routines. For that the little extension of using it during
the wait will (hopefully) not hurt.

# Conflicts:
#	Marlin/Configuration_adv.h

Make stepper shutdown after inactivity dependent on a new set of
#defines.
DISABLE_INACTIV_X
DISABLE_INACTIV_Y
DISABLE_INACTIV_Z
DISABLE_INACTIV_E

And make exemplaric Configuration.
Names can be discussed.

This makes the disabling of the steppers independent from the DISABLE_?
settings witch shut down the steppers immediately.

Introduce additional variable axis_homed to replace axix_known_position
when the coordinate display should indicate the axis is not homed.
This is to distinguish between "not homed" and "inexact position possible
because stepper was disabled".

# Conflicts:
#	Marlin/ultralcd_implementation_hitachi_HD44780.h
solved

@thinkyhead
Hi Scott,
your code from a0f362c@thinkyhead is great, but you forgot to skip the
command.
Symptom `M117 Test`shows `M117 Test` on LCD instead of `Test`.

see also
https://github.com/MarlinFirmware/Marlin/commit/a0f362c735
6f8e3c2f17 lines 941, 2851 and so on

Greetings and welcome back

Jochen

The domain is gone and doesn’t redirect, so for now show no URL on the boot screen.

This is a proposed change. This section of M114 output is a debug
extension according to RepRap wiki.

Addresses issue #2715

Send the correct line number.
If no N was in the command - non't send an N.

Replace the "ok" in M280, M301, M304, M851 with output not including an "ok"
to avoid senting two "ok"s for a single g-code.

Doing the same for M105 would break the input filters of the hosts.
For M105 the other "ok" is omitted.

Make the output of M105 more similar to Repetier.
Make the text-print pert of M105 an extra function to make it reusable. `print_heaterstates()`
Use `print_heaterstates()` in M019, M190 and M303

This is a back port of the correct in issue #248