Fix bug with phantom input windows.

Add dumpsys integration for the native input dispatcher.
Add some InputDevice API stubs.
Add an appendFormat helper method to String8 for printf style
string formatting mainly for debugging purposes.
Use generic ArrayList<WindowState> everywhere in WindowManagerService
to eliminate unnecessary casts all over.

Change-Id: I9d1e3bd90eb7222d10620200477f11b7bfd25e44