Added grbl planner Matlab simulator for test reference. Updated line number compile-time option.

- Added a grbl planner simulation tool that was written in Matlab and
Python. It was used to visualize the inner workings of the planner as a
program is streamed to it. The simulation assumes that the planner
buffer is empty, then filled, and kept filled. This is mainly for users
to see how the planner works.

- Updated some of the compile-time ifdefs when enabling line numbers.
The leaving the un-used line numbers in the function calls eats a
non-neglible amount of flash memory. So the new if-defs remove them.

planner.h

@@ -64,7 +64,11 @@ void plan_reset();
 // Add a new linear movement to the buffer. target[N_AXIS] is the signed, absolute target position 
 // in millimeters. Feed rate specifies the speed of the motion. If feed rate is inverted, the feed
 // rate is taken to mean "frequency" and would complete the operation in 1/feed_rate minutes.
+#ifdef USE_LINE_NUMBERS
 void plan_buffer_line(float *target, float feed_rate, uint8_t invert_feed_rate, int32_t line_number);
+#else
+void plan_buffer_line(float *target, float feed_rate, uint8_t invert_feed_rate);
+#endif
 
 // Called when the current block is no longer needed. Discards the block and makes the memory
 // availible for new blocks.