Minor fix related to spindle_stop() crashing abort in certain cases.

- Updated spindle_stop() to fix abort bug and to be more in line with
v0.8.

serial.c

@@ -200,4 +200,4 @@ void serial_reset_read_buffer()
   #if ENABLE_XONXOFF
     flow_ctrl = XON_SENT;
   #endif
-}  
+}