Update planner.c

Removed inline from all functions. 

If this is really needed is there another way that we can get 
around using it? (The Arduino IDE does not recognize it)

planner.c

@@ -307,14 +307,14 @@ void plan_init()
   memset(&pl, 0, sizeof(pl)); // Clear planner struct
 }
 
-inline void plan_discard_current_block() 
+void plan_discard_current_block() 
 {
   if (block_buffer_head != block_buffer_tail) {
     block_buffer_tail = next_block_index( block_buffer_tail );
   }
 }
 
-inline block_t *plan_get_current_block() 
+block_t *plan_get_current_block() 
 {
   if (block_buffer_head == block_buffer_tail) { return(NULL); }
   return(&block_buffer[block_buffer_tail]);