Hi, I'm rewriting the GRBL library for RAMPS and changing the PINS, 
however
I'm lost on the interrupts ... Is there any guide/info on how to double 
check I got it OK?

Original code
#define LIMIT_DDR       DDRB
#define LIMIT_PORT      PORTB
#define LIMIT_PIN       PINB
#define X_LIMIT_BIT     4 // MEGA2560 Digital Pin 10
#define Y_LIMIT_BIT     5 // MEGA2560 Digital Pin 11
#define Z_LIMIT_BIT     6 // MEGA2560 Digital Pin 12
#define LIMIT_INT       PCIE0  // Pin change interrupt enable pin
#define LIMIT_INT_vect  PCINT0_vect
#define LIMIT_PCMSK     PCMSK0 // Pin change interrupt register


New code - changed to PORT E
#define LIMIT_DDR       DDRE
#define LIMIT_PORT      PORTE
#define LIMIT_PIN       PINE
#define X_LIMIT_BIT     5 // MEGA2560 Digital Pin 3
#define Y_LIMIT_BIT     4 // MEGA2560 Digital Pin 2
#define Z_LIMIT_BIT     1 // MEGA2560 Digital Pin 1
#define LIMIT_INT       PCIE0  // Pin change interrupt enable pin
#define LIMIT_INT_vect  PCINT0_vect
#define LIMIT_PCMSK     PCMSK0