Restrict coincident target updates to M3 constant laser only.

- Restrict M3 forced updates when there is a motion block with a
coincident target. Force syncing of the spindle state can lead to some
pauses during a job that has coincident targets. That’s not
particularly desirable. This ensures M4 dynamic mode is not effected by
this force-sync.

doc/log/commit_log_v1.1.txt

@@ -1,3 +1,14 @@
+----------------
+Date: 2017-02-23
+Author: Sonny Jeon
+Subject: Fixed issue with M3 laser state changes and coincident targets.
+
+[fix] When in M3 constant laser power mode, a change from G0 to G1
+would not set the laser on, if G1 was passed with a coincident target.
+Motion controller now checks for a coincident target situation and will
+force a spindle sync when detected.
+
+
 ----------------
 Date: 2017-01-31
 Author: Sonny Jeon

grbl/motion_control.c

@@ -67,8 +67,11 @@ void mc_line(float *target, plan_line_data_t *pl_data)
   // Plan and queue motion into planner buffer
   if (plan_buffer_line(target, pl_data) == PLAN_EMPTY_BLOCK) {
     if (bit_istrue(settings.flags,BITFLAG_LASER_MODE)) {
-      // Correctly set laser state, if there is a coincident position passed. Forces a buffer sync.
-      spindle_sync((pl_data->condition & (PL_COND_FLAG_SPINDLE_CW|PL_COND_FLAG_SPINDLE_CCW)), pl_data->spindle_speed);
+      // Correctly set spindle state, if there is a coincident position passed. Forces a buffer
+      // sync while in M3 laser mode only.
+      if (pl_data->condition & PL_COND_FLAG_SPINDLE_CW) {
+        spindle_sync(PL_COND_FLAG_SPINDLE_CW, pl_data->spindle_speed);
+      }
     }
   }
 }