Added read() for Wire and deprecated receive()
Added Serial (both Hardware and USB) receive interrupt callback support

You can now attach an interrupt callback to the serial system which gets
called whenever a character arrives.  Example:

    void setup() {
        Serial.begin(9600);
        Serial.attachInterrupt(receive);
    }

    void loop() {
    }

    void receive(int ch) {
        Serial.write(ch);
    }

detachInterrupt() is also there for removing it.  Attaching an interrupt
disables the normal receive ring buffer.
Merge pull request #534 from UECIDE/master

Added read() for Wire and deprecated receive()