ii: use the previous buffer allocation algorithm again
ii: use the previous buffer allocation algorithm again

The algorithm is used until 7dd19103de5df2f8c0af7ac47b9149d421a0aa5d .

The algorithm is for natural language. It's suitable for natural
language but it's not good performance for some non natural language
text data. So we introduce the new buffer allocation algorithm.

But the new buffer allocation algorithm increases index size for natural
language. So we use the previous buffer allocation algorithm again just
for natural language text. We assume that target text is natural
language if lexicon has a tokenizer.

cosmo0920/groonga,cosmo0920/groonga,groonga/groonga,naoa/groonga,groonga/groonga,kenhys/groonga,naoa/groonga,kenhys/groonga,komainu8/groonga,groonga/groonga,kenhys/groonga,groonga/groonga,kenhys/groonga,kenhys/groonga,komainu8/groonga,groonga/groonga,groonga/groonga,komainu8/groonga,naoa/groonga,cosmo0920/groonga,cosmo0920/groonga,komainu8/groonga,naoa/groonga,naoa/groonga,naoa/groonga,naoa/groonga,kenhys/groonga,cosmo0920/groonga,cosmo0920/groonga,komainu8/groonga,cosmo0920/groonga,kenhys/groonga,komainu8/groonga,naoa/groonga,komainu8/groonga,cosmo0920/groonga,komainu8/groonga,kenhys/groonga,groonga/groonga,groonga/groonga