okay. _i2c.digitalWrite() is not working properly.
For example,
_i2c.digitalWrite(6, 1);
_i2c.digitalWrite(7, 1);
and
_i2c.digitalWrite(7, 1);
_i2c.digitalWrite(6, 1);
work differently on Galileo; only the second statement is valid.
_i2c.digitalWrite(7, 1);
_i2c.digitalWrite(8, 1);
and
_i2c.digitalWrite(7, 1);
_i2c.digitalWrite(8, 1);
work the same; both statements are valid.
It seems that bit handling (within byte boundary) of the library is incorrect.
Due to above error, RGB backlight on Adafruit LCD lit strange. It could be a clue to fix the library.