Improved constant laser power per rate mode. Re-factored for flash size. Minor bug fixes.

- NOTE: This commit has largely been untested.

- Constant laser power per rate mode has been improved. Altered its
implementation to be more responsive and accurate.

- Based on LaserWeb dev feedback, only G1, G2, and G3 moves operate
with constant laser power mode. Meaning that G0, G38.x, and $J jogging
motions operate without it and will keep a constant power output. This
was specifically requested as a way to focus the laser by keeping the
laser on when not moving. Operationally, this shouldn’t alter how the
laser mode operates.

- Re-factored parts of the g-code parser and g-code state reports to
save a few hundred bytes of flash. What was done makes the code a bit
more unreadable (bad), but the flash space was in dire need. So, I’m
willing to live with it for now.

- Fixed a problem with $G g-code state reports. Showed `M0` program
pause during a run state. Now fixed to show nothing during a run state.
Also, `M30` program end was shown as `M2`. This was also corrected.

- Improved spindle stop override responsiveness by removing the
enforced spindle restoring delay. It’s not needed for a feature that is
user controlled.

- Fixed a bug with G2/3 arcs in inverse time mode.

- Updated the interface.md document to make it more clear how WPos: or
MPos: can be calculated from WCO:. Some GUI devs have failed to catch
this in the documentation.

grbl/motion_control.c

@@ -106,8 +106,11 @@ void mc_arc(float *target, plan_line_data_t *pl_data, float *position, float *of
     // Multiply inverse feed_rate to compensate for the fact that this movement is approximated
     // by a number of discrete segments. The inverse feed_rate should be correct for the sum of
     // all segments.
-    if (pl_data->condition & PL_COND_FLAG_INVERSE_TIME) { pl_data->feed_rate *= segments; }
-
+    if (pl_data->condition & PL_COND_FLAG_INVERSE_TIME) { 
+      pl_data->feed_rate *= segments; 
+      bit_false(pl_data->condition,PL_COND_FLAG_INVERSE_TIME); // Force as feed absolute mode over arc segments.
+    }
+    
     float theta_per_segment = angular_travel/segments;
     float linear_per_segment = (target[axis_linear] - position[axis_linear])/segments;