Initial v0.8 ALPHA commit. Features multi-tasking run-time command execution (feed hold, cycle start, reset, status query). Extensive re-structuring of code for future features.

- ALPHA status. - Multitasking ability with run-time command executions
for real-time control and feedback. - Decelerating feed hold and resume
during operation. - System abort/reset, which immediately kills all
movement and re-initializes grbl. - Re-structured grbl to easily allow
for new features: Status reporting, jogging, backlash compensation. (To
be completed in the following releases.) - Resized TX/RX serial buffers
(32/128 bytes) - Increased planner buffer size to 20 blocks. - Updated
documentation.

spindle_control.c

@@ -20,11 +20,14 @@
 
 #include "spindle_control.h"
 #include "settings.h"
+#include "motion_control.h"
 #include "config.h"
-#include "stepper.h"
+#include "planner.h"
 
 #include <avr/io.h>
 
+// TODO: Deprecated. Need to update for new version.
+
 static int current_direction;
 
 void spindle_init()
@@ -35,7 +38,7 @@ void spindle_init()
 void spindle_run(int direction, uint32_t rpm) 
 {
   if (direction != current_direction) {
-    st_synchronize();
+    plan_synchronize();
     if(direction) {
       if(direction > 0) {
         SPINDLE_DIRECTION_PORT &= ~(1<<SPINDLE_DIRECTION_BIT);