G38.2 probe feature rough draft installed. Working but needs testing.

- G38.2 straight probe now supported. Rough draft. May be tweaked more
as testing ramps up.

- G38.2 requires at least one axis word. Multiple axis words work too.
When commanded, the probe cycle will move at the last ‘F’ feed rate
specified in a straight line.

- During a probe cycle: If the probe pin goes low (normal high), Grbl
will record that immediate position and engage a feed hold. Meaning
that the CNC machine will move a little past the probe switch point, so
keep federates low to stop sooner. Once stopped, Grbl will issue a move
to go back to the recorded probe trigger point.

- During a probe cycle: If the probe switch does not engage by the time
the machine has traveled to its target coordinates, Grbl will issue an
ALARM and the user will be forced to reset Grbl. (Currently G38.3 probe
without error isn’t supported, but would be easy to implement later.)

- After a successful probe, Grbl will send a feedback message
containing the recorded probe coordinates in the machine coordinate
system. This is as the g-code standard on probe parameters specifies.

- The recorded probe parameters are retained in Grbl memory and can be
viewed with the ‘$#’ print parameters command. Upon a power-cycle, not
a soft-reset, Grbl will re-zero these values.

- Moved ‘$#’ command to require IDLE or ALARM mode, because it accesses
EEPROM to fetch the coordinate system offsets.

- Updated the Grbl version to v0.9d.

- The probe cycle is subject to change upon testing or user-feedback.

report.h

@@ -36,11 +36,11 @@
 #define STATUS_ALARM_LOCK 12
 #define STATUS_SOFT_LIMIT_ERROR 13
 #define STATUS_OVERFLOW 14
-#define STATUS_PROBE_ERROR 15
 
 // Define Grbl alarm codes. Less than zero to distinguish alarm error from status error.
 #define ALARM_LIMIT_ERROR -1
 #define ALARM_ABORT_CYCLE -2
+#define ALARM_PROBE_FAIL -3
 
 // Define Grbl feedback message codes.
 #define MESSAGE_CRITICAL_EVENT 1
@@ -70,13 +70,11 @@ void report_grbl_settings();
 // Prints realtime status report
 void report_realtime_status();
 
-// Prints realtime position status report at the end of a probe cycle
-// This is in leiu of saving the probe position to internal variables like an 
-// EMC machine
-void report_realtime_status_probe();
+// Prints recorded probe position
+void report_probe_parameters();
 
-// Prints Grbl persistent coordinate parameters
-void report_gcode_parameters();
+// Prints Grbl NGC parameters (coordinate offsets, probe)
+void report_ngc_parameters();
 
 // Prints current g-code parser mode state
 void report_gcode_modes();