deb: enable hardening features
deb: enable hardening features

see https://wiki.debian.org/Hardening

[groonga-dev,01930]

Patch by Hideki Yamane. Thanks!!!

cosmo0920/groonga,naoa/groonga,myokoym/groonga,hiroyuki-sato/groonga,cosmo0920/groonga,myokoym/groonga,komainu8/groonga,kenhys/groonga,myokoym/groonga,kenhys/groonga,naoa/groonga,redfigure/groonga,redfigure/groonga,komainu8/groonga,groonga/groonga,groonga/groonga,groonga/groonga,hiroyuki-sato/groonga,hiroyuki-sato/groonga,myokoym/groonga,cosmo0920/groonga,redfigure/groonga,komainu8/groonga,naoa/groonga,myokoym/groonga,kenhys/groonga,komainu8/groonga,hiroyuki-sato/groonga,kenhys/groonga,hiroyuki-sato/groonga,redfigure/groonga,komainu8/groonga,naoa/groonga,myokoym/groonga,redfigure/groonga,myokoym/groonga,naoa/groonga,naoa/groonga,redfigure/groonga,myokoym/groonga,groonga/groonga,naoa/groonga,komainu8/groonga,kenhys/groonga,cosmo0920/groonga,cosmo0920/groonga,groonga/groonga,groonga/groonga,groonga/groonga,redfigure/groonga,kenhys/groonga,hiroyuki-sato/groonga,groonga/groonga,komainu8/groonga,hiroyuki-sato/groonga,naoa/groonga,hiroyuki-sato/groonga,cosmo0920/groonga,cosmo0920/groonga,komainu8/groonga,kenhys/groonga,redfigure/groonga,kenhys/groonga,cosmo0920/groonga