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

config.h

@@ -69,9 +69,9 @@
 #define COOLANT_FLOOD_PORT  PORTC
 #define COOLANT_FLOOD_BIT   3  // Uno Analog Pin 3
 
-// #define ENABLE_M7  // Mist coolant disabled by default. Uncomment to enable.
 // NOTE: Uno analog pins 4 and 5 are reserved for an i2c interface, and may be installed at
 // a later date if flash and memory space allows.
+// #define ENABLE_M7  // Mist coolant disabled by default. Uncomment to enable.
 #ifdef ENABLE_M7
   #define COOLANT_MIST_DDR   DDRC
   #define COOLANT_MIST_PORT  PORTC
@@ -158,6 +158,18 @@
 // time step. Also, keep in mind that the Arduino delay timer is not very accurate for long delays.
 #define DWELL_TIME_STEP 50 // Integer (1-255) (milliseconds)
 
+// If homing is enabled, homing init lock sets Grbl into an alarm state upon power up. This forces
+// the user to perform the homing cycle (or override the locks) before doing anything else. This is
+// mainly a safety feature to remind the user to home, since position is unknown to Grbl.
+#define HOMING_INIT_LOCK // Comment to disable
+
+// The homing cycle seek and feed rates will adjust so all axes independently move at the homing
+// seek and feed rates regardless of how many axes are in motion simultaneously. If disabled, rates
+// are point-to-point rates, as done in normal operation. For example in an XY diagonal motion, the
+// diagonal motion moves at the intended rate, but the individual axes move at 70% speed. This option
+// just moves them all at 100% speed.
+#define HOMING_RATE_ADJUST // Comment to disable
+
 // Number of homing cycles performed after when the machine initially jogs to limit switches.
 // This help in preventing overshoot and should improve repeatability. This value should be one or 
 // greater.
@@ -167,7 +179,7 @@
 // and addresses are defined in settings.h. With the current settings, up to 5 startup blocks may
 // be stored and executed in order. These startup blocks would typically be used to set the g-code
 // parser state depending on user preferences.
-#define N_STARTUP_LINE 3 // Integer (1-5)
+#define N_STARTUP_LINE 2 // Integer (1-5)
 
 // ---------------------------------------------------------------------------------------
 // FOR ADVANCED USERS ONLY: