v1.1f. Parking override control. Spindle enable pin option.

[ver] v1.1f update due to tweaks to interface from new parking override
control.

[new] Parking motion override control via new `M56 P0` and `M56 P1`
command, which disables and enables the parking motion, respectively.
Requires ENABLE_PARKING_OVERRIDE_CONTROL and PARKING_ENABLE enabled in
config.h. Primarily for OEMs.

[new] `M56` appears in the $G report when enabled.

[new] Five new build info identification letters. Some were missing and
a couple are new. Updated the CSV and documentation to reflect these
new items.

[new] Spindle enable pin configuration option to alter its behavior
based on how certain lasers work. By default, Grbl treats the enable
pin separately and leaves it on when S is 0. The new option turns the
enable pin on and off with S>0 and S=0. This only is in effect when a
user enables the USE_SPINDLE_DIR_AS_ENABLE_PIN option.

[fix] M4 is now allowed to work when USE_SPINDLE_DIR_AS_ENABLE_PIN is
enabled. Previously this was blocked and was problematic for laser
folks using M4.

[fix] Properly declared system variables as extern. Not sure how that
went unnoticed or why it worked up until now but it has.

[fix] EXTREMELY RARE. When AMASS is intentionally disabled and sent a
motion command that is _one step_ in length, Grbl would not actuate the
step due to numerical round-off. Applied a fix to prevent the round-off
issue.

[fix] Added a compile-time check for AMASS settings to make sure that
the numerical round-off issue doesn’t effect it. This would only happen
if someone set AMASS max levels to zero. It does not effect AMASS with
its current defaults.

[fix] Wrapped the mc_parking_motion() function in an ifdef for porting
purposes.

[fix] Fixed an issue when in inverse time mode and G0’s would require a
F word. This was not correct.

[fix] Added a note in the defaults.h file that MAX_TRAVEL values must
be positive. Some users were setting this negative and it was causing
issues.

grbl/motion_control.h

@@ -54,6 +54,9 @@ void mc_homing_cycle(uint8_t cycle_mask);
 // Perform tool length probe cycle. Requires probe switch.
 uint8_t mc_probe_cycle(float *target, plan_line_data_t *pl_data, uint8_t parser_flags);
 
+// Handles updating the override control state.
+void mc_override_ctrl_update(uint8_t override_state);
+
 // Plans and executes the single special motion case for parking. Independent of main planner buffer.
 void mc_parking_motion(float *parking_target, plan_line_data_t *pl_data);