Implemented operator bool() in trie class.
Implemented operator bool() in trie class.

git-svn-id: 8ebd3ec5d1ed167a3b1d8bf7eeabef177b5f3d8d@16 7fce0ed0-c134-4a74-bdef-6e0e9c9ada2e

chokkan/dastrie,chokkan/dastrie,chokkan/dastrie