Fixed unintended laser mode pausing. Updated documentation. Min SS OVR lowered to 10%.

- [laser] Tested a working version and pushed the wrong one for the
last! 20161203 was pausing upon every spindle speed change. That’s not
right. Fixed so nearly all motions are passed through and does not stop.

- Minimum spindle speed override lower from 50% to 10%. Lasers could
use the lower speeds.

- Fixed a very minor bug related to G80 error checking. Allowed no
error with non-modal motions with axis words. Not correct and fixed.

- Fixed a compile error when disabling VARIABLE_SPINDLE

- [doc] Updated some obsolete documentation.

- [doc] Started a “Laser Mode” document that summarizes how Grbl’s new
laser mode works.

doc/markdown/change_summary.md

@@ -90,9 +90,8 @@ On a final note, these interface tweaks came about out of necessity, because mor
   - Overrides are included in every 10 or 20 status reports (configurable) depending on what Grbl is doing or, if an override value or toggle state changes, automatically in the next report.
   - There are two override fields:
     - `Ov:100,100,100` Organized as feed, rapid, and spindle speed overrides in percent.
-    - `T:SFM` with each letter `S`, `F`, and `M` are defined as spindle stop active, flood coolant toggled, and mist coolant toggled, respectively.
-
-
+    
+- Accessory states are shown alongside override reports when they are active. Like pin states, an accessory state report `A:SFM` contains a letter indicating an active accessory. Letters `S`, `C`, `F`, and `M` are defined as spindle CW, spindle CCW, flood coolant, and mist coolant, respectively. The pins are directly polled and shown here.
 
 - Line numbers, when enabled in config.h, are omitted when: