- Rename WRITE_E_STEP for consistency

- Add BIT and TEST macros
- Add _APPLY_ macros to stepper.cpp to help with consolidation
- Consolidate code in stepper.cpp using macros
- Apply standards in stepper.cpp
- Use >= 0 instead of > -1 as a better semantic
- Replace DUAL_Y_CARRIAGE with Y_DUAL_STEPPER_DRIVERS

Marlin/MarlinSerial.h

@@ -97,14 +97,14 @@ class MarlinSerial { //: public Stream
     }
 
     FORCE_INLINE void write(uint8_t c) {
-      while (!((M_UCSRxA) & (1 << M_UDREx)))
+      while (!TEST(M_UCSRxA, M_UDREx))
         ;
 
       M_UDRx = c;
     }
 
     FORCE_INLINE void checkRx(void) {
-      if ((M_UCSRxA & (1<<M_RXCx)) != 0) {
+      if (TEST(M_UCSRxA, M_RXCx)) {
         unsigned char c  =  M_UDRx;
         int i = (unsigned int)(rx_buffer.head + 1) % RX_BUFFER_SIZE;