Re-factored system states and alarm management. Serial baud support greater than 57600.

- Refactored system states to be more clear and concise. Alarm locks
processes when position is unknown to indicate to user something has
gone wrong.

- Changed mc_alarm to mc_reset, which now manages the system reset
function. Centralizes it.

- Renamed '$X' kill homing lock to kill alarm lock.

- Created an alarm error reporting method to clear up what is an alarm:
message vs a status error: message. For GUIs mainly. Alarm codes are
negative. Status codes are positive.

- Serial baud support upto 115200. Previous baudrate calc was unstable
for 57600 and above.

- Alarm state locks out all g-code blocks, including startup scripts,
but allows user to access settings and internal commands. For example,
to disable hard limits, if they are problematic.

- Hard limits do not respond in an alarm state.

- Fixed a problem with the hard limit interrupt during the homing
cycle. The interrupt register is still active during the homing cycle
and still signal the interrupt to trigger when re-enabled. Instead,
just disabled the register.

- Homing rate adjusted. All axes move at homing seek rate, regardless
of how many axes move at the same time. This is unlike how the stepper
module does it as a point to point rate.

- New config.h settings to disable the homing rate adjustment and the
force homing upon powerup.

- Reduced the number of startup lines back down to 2 from 3. This
discourages users from placing motion block in there, which can be very
dangerous.

- Startup blocks now run only after an alarm-free reset or after a
homing cycle. Does not run when $X kill is called. For satefy reasons

gcode.c

@@ -84,6 +84,11 @@ static float to_millimeters(float value)
 // internal functions in terms of (mm, mm/min) and absolute machine coordinates, respectively.
 uint8_t gc_execute_line(char *line) 
 {
+
+  // If in alarm state, don't process. Immediately return with error.
+  // NOTE: Might not be right place for this, but also prevents $N storing during alarm.
+  if (sys.state == STATE_ALARM) { return(STATUS_ALARM_LOCK); }
+ 
   uint8_t char_counter = 0;  
   char letter;
   float value;
@@ -545,7 +550,7 @@ uint8_t gc_execute_line(char *line)
     
     // If complete, reset to reload defaults (G92.2,G54,G17,G90,G94,M48,G40,M5,M9). Otherwise,
     // re-enable program flow after pause complete, where cycle start will resume the program.
-    if (gc.program_flow == PROGRAM_FLOW_COMPLETED) { sys.execute |= EXEC_RESET; }
+    if (gc.program_flow == PROGRAM_FLOW_COMPLETED) { mc_reset(); }
     else { gc.program_flow = PROGRAM_FLOW_RUNNING; }
   }