vector: don't use "auto" for old g++ on CentOS 6
vector: don't use "auto" for old g++ on CentOS 6

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