Log Message:
mozc: Fix build under NetBSD/i386 and use external protobuf library

* Include mk/atomic64.mk to add -march=i586 to CFLAGS and pass
  CFLAGS to gyp. Fix PR pkg/56025 in another way.
* Use external devel/protobuf to avoid internal protobuf build.
  So bump PKGREVISION.
* dictionary/pos_matcher.h does not generated before its use sometimes.
  Generate it explicitly with
  dictionary/dictionary_base.gyp:text_dictionary_loader target
  for mozc-server.