That is one library I've come to wish was just in Core and perhaps lower level capabilities like getting current state and some Android versions (Gingerbread and before) tend to not fire the height change event all the time, so some way of getting normal screen size/keyboard screen size/which mode currently in would be good.
Adding the IME library to the Core library will just make the Core library a little bit larger. There is no difference between external libraries and the core library.