http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54419
--- Comment #45 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-09-06 14:58:25 UTC --- Well, it is using autotools, the decision whether to put the stuff into autoinclude.m4 and reference in configure.ac, or put in full just into configure.ac is pure esthetical thing.