highlighter: reuse created patricia trie for performance
highlighter: reuse created patricia trie for performance

It may be better that we remove all existing records on many keywords
case.

komainu8/groonga,kenhys/groonga,naoa/groonga,naoa/groonga,groonga/groonga,naoa/groonga,naoa/groonga,kenhys/groonga,naoa/groonga,komainu8/groonga,komainu8/groonga,groonga/groonga,kenhys/groonga,kenhys/groonga,groonga/groonga,kenhys/groonga,komainu8/groonga,groonga/groonga,komainu8/groonga,naoa/groonga,komainu8/groonga,kenhys/groonga,groonga/groonga,komainu8/groonga,naoa/groonga,groonga/groonga,kenhys/groonga,kenhys/groonga,groonga/groonga,groonga/groonga,naoa/groonga,komainu8/groonga