TwoWire to support running as I2C Slave, responding to multiple IDs

[hattesen]

The class TwoWire interface should be updates to operate as I2C Slave responding to multiple Slave IDs.

Header (class TwoWire [Sic!]) file: Wire.h

Implementation file: Wire.cpp

Proposed implementation design

void begin(uint8_t);

Should be overloaded with one, or both, of these alternatives:

// Starting as I2C Slave, responding when the bus master addresses any one of the IDs contained in the slave_ID[]
void begin(uint8_t const* slave_id[]);

// Starting as I2C Slave, responding when the bus master addresses an ID to which the `idPtr(uint8_t const slaveID)` responds `!=0`
bool (*idPtr)(uint8_t const slaveID);