Binding 4 relays to port C and adding logic

[pusso]

Hello, my commit requared 2560 processor in config.h
// Default cpu mappings. Grbl officially supports the Arduino Uno only. Other processor types
// may exist from user-supplied templates or directly user-defined in cpu_map.h
//#define CPU_MAP_ATMEGA328P // Arduino Uno CPU

define CPU_MAP_ATMEGA2560 // Arduino MEGA 2560 CPU

For relays i was use 4 pins of MEGA for port C

+#define RELAY_DDR DDRC
+#define RELAY_PORT PORTC
+#define RELAY1_BIT 3 // Pin 37
+#define RELAY2_BIT 2 // Piin 36
+#define RELAY3_BIT 1 // Pin 35
+#define RELAY4_BIT 0 // Pin 34
Thanx for all.

[chamnit]

@pusso : Thanks for the pull request. I will be moving the Mega2560 development to another repository in the next few weeks. It's becoming difficult to keep the 328p code separate from the Mega code, as I'll be working on the latter more and more. I'll integrate your code there.

[pusso]

My father will use your library in his project. I think I will have the opportunity to add something into your library.