New configuration options.

- New configuration option at compile-time:
 - Force alarm upon power-up or hard reset. When homing is enabled,
this is already the default behavior. This simply forces this all of
the time.
 - GUI reporting mode. Removes most human-readable strings that GUIs
don’t need. This saves nearly 2KB in flash space that can be used for
other features.
 - Hard limit force state check: In the hard limit pin change ISR, Grbl
by default sets the hard limit alarm upon any pin change to guarantee
the alarm is set. If this option is set, it’ll check the state within
the ISR, but can’t guarantee the pin will be read correctly if the
switch is bouncing. This option makes hard limit behavior a little less
annoying if you have a good buffered switch circuit that removes
bouncing and electronic noise.

- Software debounce bug fix. It was reading the pin incorrectly for the
setting.

- Re-factored some of the ‘$’ settings code.

grbl/grbl.h

@@ -22,8 +22,8 @@
 #define grbl_h
 
 // Grbl versioning system
-#define GRBL_VERSION "0.9h"
-#define GRBL_VERSION_BUILD "20150215"
+#define GRBL_VERSION "0.9i"
+#define GRBL_VERSION_BUILD "20150223"
 
 // Define standard libraries used by Grbl.
 #include <avr/io.h>