Refactored offset handling, for improved readability and in preparation for rotation support.

Added experimental support for G66 (modal macro call) and G67 (end modal macro call).
Made axis letter to axis/motor assignment for axes ABCUVW freely changeable at compile time.
Fix for some G65 arguments being incorrectly validated for normal use (sign, range).
Added repeat support to G65 macro call via the optional L parameter word.
Changed default setting for ABC-axes to rotary.
Changed defaults for jerk settings to 10x acceleration settings.
Disabled jerk for jog, probe and spindle synchronized motion.
Added _active_probe system parameter, returns -1 if no probe inputs available.
Minor bug fix, G5.1 and G33.1 motion commands were not coverted to the correct string equivalent in $G output.

plugins_init.h

@@ -3,7 +3,7 @@
 
   Calls the init function of enabled plugins, may be included at the end of the drivers driver_init() implementation.
 
-  These are NOT referenced in the core grbl code
+  These are NOT referenced in the core grblHAL code
 
   Part of grblHAL
 
@@ -166,7 +166,7 @@
     embroidery_init();
 #endif
 
-#if RGB_LED_ENABLE
+#if RGB_LED_ENABLE > 1
     extern void rgb_led_init (void);
     rgb_led_init();
 #endif
@@ -239,10 +239,14 @@
 #endif
 
 #if ATCI_ENABLE
-  extern void atci_init(void);
+  extern void atci_init (void);
   atci_init();
 #endif
 
+#if M800_ENABLE
+  extern void keyway_init (void);
+  keyway_init();
+#endif
 
 // End third party plugin definitions.