Major g-code parser overhaul. 100%* compliant. Other related updates.

- Completely overhauled the g-code parser. It’s now 100%* compliant. (*
may have some bugs). Being compliant, here are some of the major
differences.

- SMALLER and JUST AS FAST! A number of optimizations were found that
sped things up and allowed for the more thorough error-checking to be
installed without a speed hit. Trimmed a lot of ‘fat’ in the parser and
still was able to make it significantly smaller than it was.

- No default feed rate setting! Removed completely! This doesn’t exist
in the g-code standard. So, it now errors out whenever it’s undefined
for motions that require it (G1/2/3/38.2).

- Any g-code parser error expunges the ENTIRE block. This means all
information is lost and not passed on to the running state. Before some
of the states would remain, which could have led to some problems.

- If the g-code block passes all of the error-checks, the g-code state
is updated and all motions are executed according to the order of
execution.

- Changes in spindle speed, when already running, will update the
output pin accordingly. This fixes a bug, where it wouldn’t update the
speed.

- Update g-code parser error reporting. Errors now return detailed
information of what exact went wrong. The most common errors return a
short text description. For less common errors, the parser reports
‘Invalid gcode ID:20’, where 20 is a error ID. A list of error code IDs
and their descriptions will be documented for user reference elsewhere
to save flash space.

- Other notable changes:

- Added a print integer routine for uint8 variables. This saved
significant flash space by switching from a heavier universal print
integer routine.

- Saved some flash space with our own short hypotenuse calculation

- Some arc computation flash and memory optimizations.

probe.c

@@ -30,13 +30,19 @@ void probe_init()
 }
 
 
+// Returns the probe pin state. Triggered = true. Called by gcode parser and probe state monitor.
+uint8_t probe_get_state()
+{
+  return(!(PROBE_PIN & PROBE_MASK));
+}
+
 // Monitors probe pin state and records the system position when detected. Called by the
 // stepper ISR per ISR tick.
 // NOTE: This function must be extremely efficient as to not bog down the stepper ISR.
 void probe_state_monitor()
 {
   if (sys.probe_state == PROBE_ACTIVE) { 
-    if (!(PROBE_PIN & PROBE_MASK)) {
+    if (probe_get_state()) {
       sys.probe_state = PROBE_OFF;
       memcpy(sys.probe_position, sys.position, sizeof(float)*N_AXIS);
       sys.execute |= EXEC_FEED_HOLD;