Minor updates to line number feature.

- Changed line number integer types from unsigned to signed int32.
G-code mandates values cannot exceed 99999. Negative values can be used
to indicate certain modes.

- Homing cycle line number changed to -1, as an indicator.

- Fixed a reporting define for the spindle states that was broken by
the last merge.

planner.c

@@ -259,7 +259,7 @@ 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). */
-void plan_buffer_line(float *target, float feed_rate, uint8_t invert_feed_rate, uint32_t line_number) 
+void plan_buffer_line(float *target, float feed_rate, uint8_t invert_feed_rate, int32_t line_number) 
 {
   // Prepare and initialize new block
   plan_block_t *block = &block_buffer[block_buffer_head];
@@ -267,9 +267,10 @@ void plan_buffer_line(float *target, float feed_rate, uint8_t invert_feed_rate,
   block->millimeters = 0;
   block->direction_bits = 0;
   block->acceleration = SOME_LARGE_VALUE; // Scaled down to maximum acceleration later
-#ifdef USE_LINE_NUMBERS
-  block->line_number = line_number;
-#endif
+  #ifdef USE_LINE_NUMBERS
+    block->line_number = line_number;
+  #endif
+
   // Compute and store initial move distance data.
   // TODO: After this for-loop, we don't touch the stepper algorithm data. Might be a good idea
   // to try to keep these types of things completely separate from the planner for portability.