Implement ver4 dictionary unigram writing methods.

native/jni/Android.mk

...ictionary/structure/v4/content/probability_dict_content.h

...ary/structure/v4/content/terminal_position_lookup_table.h

...st/policyimpl/dictionary/structure/v4/ver4_dict_buffers.h

...olicyimpl/dictionary/structure/v4/ver4_dict_constants.cpp

.../policyimpl/dictionary/structure/v4/ver4_dict_constants.h

...ictionary/structure/v4/ver4_patricia_trie_node_writer.cpp

.../dictionary/structure/v4/ver4_patricia_trie_node_writer.h

...mpl/dictionary/structure/v4/ver4_patricia_trie_policy.cpp

...yimpl/dictionary/structure/v4/ver4_patricia_trie_policy.h

.../android/inputmethod/latin/Ver4BinaryDictionaryTests.java