Merge "Add dictionary header writing methods."

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

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

...yimpl/dictionary/dynamic_patricia_trie_writing_helper.cpp

...icyimpl/dictionary/dynamic_patricia_trie_writing_helper.h

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

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

...est/policyimpl/dictionary/header/header_reading_utils.cpp

...ggest/policyimpl/dictionary/header/header_reading_utils.h

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

.../src/suggest/policyimpl/dictionary/utils/format_utils.cpp

...ni/src/suggest/policyimpl/dictionary/utils/format_utils.h

.../com/android/inputmethod/latin/BinaryDictionaryTests.java