Push old dev_2 draft to work on other things.

- **NON-FUNCTIONAL**
- Contains an old draft of separating the stepper driver direct access
to the planner buffer. This is designed to keep the stepper and planner
modules independent and prevent overwriting or other complications. In
this way, feedrate override should be able to be installed as well.
- A number of planner optimizations are installed too.
- Not sure where the bugs are. Either in the new planner optimizations,
new stepper module updates, or in both. Or it just could be that the
Arduino AVR is choking with the new things it has to do.

nuts_bolts.c

@@ -140,9 +140,16 @@ void delay_us(uint32_t us)
   }
 }
 
-// Syncs all internal position vectors to the current system position.
-void sys_sync_current_position()
+
+// Returns direction mask according to Grbl internal axis indexing.
+uint8_t get_direction_mask(uint8_t axis_idx)
 {
-  plan_set_current_position(sys.position[X_AXIS],sys.position[Y_AXIS],sys.position[Z_AXIS]);
-  gc_set_current_position(sys.position[X_AXIS],sys.position[Y_AXIS],sys.position[Z_AXIS]);
+  uint8_t axis_mask = 0;
+  switch( axis_idx ) {
+    case X_AXIS: axis_mask = (1<<X_DIRECTION_BIT); break;
+    case Y_AXIS: axis_mask = (1<<Y_DIRECTION_BIT); break;
+    case Z_AXIS: axis_mask = (1<<Z_DIRECTION_BIT); break;
+  }
+  return(axis_mask);
 }
+