Corrections to I2C code:
1) I2CManager_Mega4809.h: Correct bitwise 'and' to logical 'and' - no impact.
2) I2CManager_Wire.h: Ensure that error codes from Wire subsystem are passed back to caller in queueRequest().
* Re-enable native I2C driver.
* Minor non-functional changes to native I2C Manager.
* Minor changes to make variable types explicit in comparisons.
* Fix IODevice::loop() to avoid null pointer dereference.
Strange problems with LCD driver tracked down to being caused by a call to p->_loop() when p is NULL.
* Correct sense of comparison in LCN support function Turnout::setClosedStateOnly()
* Remove code (now unused) from LCD driver.
* Add I2C textual error messages.
* Add I2C textual error messages.
* Fix compile error in 4809 I2C driver.
* Remove init function call from SSD1306 driver.
