Fix for Due Wire library

[bluesign2k]

Fix reading and use of TWI status register.
Also, update endTransmission to be compatible with original & give more useful return values.

[Lauszus]

Note this closes: #1976.

[bluesign2k]

The latest two commits should be ignored... forgot to make a new branch so it got merged with this pull. Oops.

The original commit to add compatibility still stands.

[bluesign2k]

FWIW. This also enables polling of devices of device on the bus. A basic example...

uint8_t I2C_DevicePoll(uint8_t device_addr) {
    uint32_t timeout = millis();

    while (1) {
        Wire.beginTransmission(device_addr);
        Wire.write(0x00);
        if (!Wire.endTransmission(true)) break;

        if ((millis() - timeout) > I2C_TIMEOUT) return 1;
    }
    return 0;
}

[odbol]

I have tested this with an 24LC64B EEPROM and it works! The I2CScanner finally detects my device properly now. Thank you @bluesign2k

I wrote some read/write tests which passed and are available here: https://github.com/odbol/EEPROM_I2C

Can we please merge this in ASAP?

[cmaglie]

I've manually merged the relevant commit here:

e079baa

Thank you!