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.c

@@ -259,7 +259,11 @@ uint8_t plan_check_full_buffer()
    is used in three ways: as a normal feed rate if invert_feed_rate is false, as inverse time if
    invert_feed_rate is true, or as seek/rapids rate if the feed_rate value is negative (and
    invert_feed_rate always false). */
+#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
 {
   // Prepare and initialize new block
   plan_block_t *block = &block_buffer[block_buffer_head];