Straighten the dead char implementation, take 3.

java/src/com/android/inputmethod/event/DeadKeyCombiner.java

java/src/com/android/inputmethod/event/Event.java

java/src/com/android/inputmethod/latin/Constants.java

.../src/com/android/inputmethod/latin/utils/StringUtils.java

...om/android/inputmethod/latin/InputLogicTestsDeadKeys.java