Individual control pin invert compile-option.

- Control pins may be individually inverted through a
CONTROL_INVERT_MASK macro. This mask is define in the cpu_map.h file.

grbl/cpu_map/cpu_map_atmega2560.h

@@ -108,6 +108,7 @@
 #define CONTROL_INT_vect  PCINT2_vect
 #define CONTROL_PCMSK     PCMSK2 // Pin change interrupt register
 #define CONTROL_MASK ((1<<RESET_BIT)|(1<<FEED_HOLD_BIT)|(1<<CYCLE_START_BIT)|(1<<SAFETY_DOOR_BIT))
+#define CONTROL_INVERT_MASK CONTROL_MASK // May be re-defined to only invert certain control pins.
 
 // Define probe switch input pin.
 #define PROBE_DDR       DDRK

grbl/cpu_map/cpu_map_atmega328p.h

@@ -117,6 +117,7 @@
 #define CONTROL_INT_vect  PCINT1_vect
 #define CONTROL_PCMSK     PCMSK1 // Pin change interrupt register
 #define CONTROL_MASK ((1<<RESET_BIT)|(1<<FEED_HOLD_BIT)|(1<<CYCLE_START_BIT)|(1<<SAFETY_DOOR_BIT))
+#define CONTROL_INVERT_MASK CONTROL_MASK // May be re-defined to only invert certain control pins.
   
 // Define probe switch input pin.
 #define PROBE_DDR       DDRC