Bug fix for certain motions. Re-org of includes.

- Critical bug fix for diagonal motions that continue on the same
direction or return in the exact opposite direction. This issue could
cause Grbl to crash intermittently due to a numerical round-off error.
Grbl versions prior to v0.9g shouldn’t have this issue.

- Reorganized all of the includes used by Grbl. Centralized it into a
single “grbl.h” include. This will help simplify the compiling and
uploading process through the Arduino IDE.

- Added an example .INO file for users to simply open and run when
compiling and uploading through the IDE. More to come later.

grbl.h

@@ -25,25 +25,41 @@
 #ifndef grbl_h
 #define grbl_h
 
-// All of the Grbl system include files.
+#define GRBL_VERSION "0.9h"
+#define GRBL_VERSION_BUILD "20150210"
+
+// Define standard libraries used by Grbl.
+#include <avr/io.h>
+#include <avr/pgmspace.h>
+#include <avr/interrupt.h>
+#include <avr/wdt.h>
+#include <util/delay.h>
+#include <math.h>
+#include <inttypes.h>    
+#include <string.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <stdbool.h>
+
+// Define the Grbl system include files.
 #include "config.h"
-#include "coolant_control.h"
-#include "cpu_map.h"
+#include "nuts_bolts.h"
+#include "settings.h"
+#include "system.h"
 #include "defaults.h"
+#include "cpu_map.h"
+#include "coolant_control.h"
 #include "eeprom.h"
 #include "gcode.h"
 #include "limits.h"
 #include "motion_control.h"
-#include "nuts_bolts.h"
 #include "planner.h"
 #include "print.h"
 #include "probe.h"
 #include "protocol.h"
 #include "report.h"
 #include "serial.h"
-#include "settings.h"
 #include "spindle_control.h"
 #include "stepper.h"
-#include "system.h"
 
 #endif