Merge branch 'dev_2' into dev

Conflicts:
README.md
gcode.c
motion_control.c
planner.c
planner.h
protocol.c
report.c
settings.c
settings.h
stepper.c
stepper.h

serial.c

@@ -91,11 +91,7 @@ void serial_write(uint8_t data) {
 }
 
 // Data Register Empty Interrupt handler
-#ifdef __AVR_ATmega644P__
-ISR(USART0_UDRE_vect)
-#else
-ISR(USART_UDRE_vect)
-#endif
+ISR(SERIAL_UDRE)
 {
   // Temporary tx_buffer_tail (to optimize for volatile)
   uint8_t tail = tx_buffer_tail;
@@ -144,11 +140,7 @@ uint8_t serial_read()
   }
 }
 
-#ifdef __AVR_ATmega644P__
-ISR(USART0_RX_vect)
-#else
-ISR(USART_RX_vect)
-#endif
+ISR(SERIAL_RX)
 {
   uint8_t data = UDR0;
   uint8_t next_head;