Bug fixes and more limit configurability

- Strange sizeof() bug in the most recent releases. Manifested as an
alarm upon a power up even when homing was disabled. Fixed by declaring
sizeof() with struct types, rather than variable names, even though
they were validated to give the same value.

- Spindle speed zero should disable the spindle. Now fixed.

- New configuration option for inverting certain limit pins. Handy for
mixed NO and NC switch machines. See config.h for details.

- Incremented version and pre-build firmware link.

doc/log/commit_log_v0.9j.txt

@@ -1,3 +1,19 @@
+----------------
+Date: 2015-12-18
+Author: Sonny Jeon
+Subject: Minor bug fixes.
+
+- Planner was under-estimating maximum speeds through straight
+junctions in certain cases. The calculations have been updated to be
+more accurate.
+
+- Type declaration fix in probe.c.
+
+ - Commit log for v0.9j generated separately from v0.9i’s.
+
+- Incremented version and updated pre-built firmware link.
+
+
 ----------------
 Date: 2015-09-30
 Author: Sonny Jeon