Our testing framework uses a special i18n "poisoned localization"
feature to find messages that ought to stay constant but are
incorrectly marked to be translated.  This feature has been made
into a runtime option (it used to be a compile-time option).

* ab/dynamic-gettext-poison:
  Makefile: ease dynamic-gettext-poison transition
  i18n: make GETTEXT_POISON a runtime option