check if PKG_CHECK_MODULES is defined
check if PKG_CHECK_MODULES is defined

this fixes the problem that configure made from autogen.sh
on OS X Lion stops while detecting KyTea.

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