Fixed homing fail alarm handling. Re-integrated software debouncing.

- [bug] Fixed a homing fail issue, where the alarm was not being set
right, not cleared correctly. It would report the wrong code and enter
an infinite alarm loop. This was due to how alarm codes were altered a
while back. Now updated and fixed to show the right codes.

- [feature] Re-installed optional software debouncing for hard limit
switches. By request.

doc/log/commit_log_v1.1.txt

@@ -1,3 +1,15 @@
+----------------
+Date: 2016-12-18
+Author: Sonny Jeon
+Subject: Addressed optional PWM min value issue. Updated docs.
+
+- [fix] Spindle PWM minimum value had some typos. Fixed the macros to
+compile correctly. Only effects users that enable SPINDLE_MINIMUM_PWM.
+The name changed to SPINDLE_PWM_MIN_VALUE for consistency sake.
+
+- Updated the laser documentation.
+
+
 ----------------
 Date: 2016-12-12
 Author: Sonny Jeon