Prepare dictionary decay.

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

...android/inputmethod/latin/ExpandableBinaryDictionary.java

...ve/jni/com_android_inputmethod_latin_BinaryDictionary.cpp

native/jni/src/suggest/core/dictionary/dictionary.cpp

native/jni/src/suggest/core/dictionary/dictionary.h

...est/core/policy/dictionary_structure_with_buffer_policy.h

...l/dictionary/dynamic_patricia_trie_gc_event_listeners.cpp

...mpl/dictionary/dynamic_patricia_trie_gc_event_listeners.h

...st/policyimpl/dictionary/dynamic_patricia_trie_policy.cpp

...gest/policyimpl/dictionary/dynamic_patricia_trie_policy.h

...yimpl/dictionary/dynamic_patricia_trie_writing_helper.cpp

...rc/suggest/policyimpl/dictionary/header/header_policy.cpp

.../src/suggest/policyimpl/dictionary/header/header_policy.h

.../src/suggest/policyimpl/dictionary/patricia_trie_policy.h

...licyimpl/dictionary/utils/buffer_with_extendable_buffer.h

...t/policyimpl/dictionary/utils/dict_file_writing_utils.cpp