Minor bug fixes.

- G38.x was not printing correctly in the $G g-code state reports. Now
fixed.

- Potential bug regarding volatile variables inside a struct. It has
never been a problem in v0.9, but ran into this during v1.0
development. Just to be safe, the fixes are applied here.

- Updated pre-built firmwares with these two bug fixes.

grbl/main.c

@@ -77,8 +77,8 @@ int main(void)
 
     // Reset system variables.
     sys.abort = false;
-    sys.rt_exec_state = 0;
-    sys.rt_exec_alarm = 0;
+    sys_rt_exec_state = 0;
+    sys_rt_exec_alarm = 0;
     sys.suspend = false;
           
     // Start Grbl main loop. Processes program inputs and executes them.