Get rid of Key.needsSpecialPopupHint and related

java/src/com/android/inputmethod/keyboard/Key.java

...rc/com/android/inputmethod/keyboard/KeyboardSwitcher.java

java/src/com/android/inputmethod/keyboard/KeyboardView.java

java/src/com/android/inputmethod/keyboard/LatinKeyboard.java

...c/com/android/inputmethod/keyboard/LatinKeyboardView.java

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