Log Message:
Update libdatrie to 0.2.4.

0.2.4 (2010-06-30)
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- Close file on saving trie. [Bug report from Xu Jiandong]
- Add trie_store_if_absent() API which fails on adding duplicated key.
  This is useful for preventing race condition in multi-thread applications.
  [Suggestion from Dan Searle]
- Add trie_fread() and trie_fwrite() APIs for reading/writing trie data in
  an open file, allowing trie to be embeded as part of a bigger file.
  [Suggestion from NIIBE Yutaka]