Log Message:
Update libdatrie to 0.2.6.

0.2.6 (2013-01-23)
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- New API trie_state_walkable_chars() for breadth-first traversal.
- New class TrieIterator for callback-free enumeration.
- Improved performance on key enumeration.
- Improved AlphaMap range merging.
- Bug fixes.
[Many thanks to Mikhail Korobov for improvements in this version.]