- 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/Marlin.h

@@ -32,6 +32,9 @@
   #include "WProgram.h"
 #endif
 
+#define BIT(b) (1<<(b))
+#define TEST(n,b) ((n)&BIT(b)!=0)
+
 // Arduino < 1.0.0 does not define this, so we need to do it ourselves
 #ifndef analogInputToDigitalPin
   #define analogInputToDigitalPin(p) ((p) + 0xA0)