Merge "Implement ver4 shortcut reading method."

...olicyimpl/dictionary/shortcut/ver4_shortcut_list_policy.h

...mpl/dictionary/structure/v4/content/bigram_dict_content.h

...l/dictionary/structure/v4/content/shortcut_dict_content.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

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

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

...cyimpl/dictionary/utils/buffer_with_extendable_buffer.cpp

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