Hi Norbert -- I don't know if automake-1.15 is a hard requirement, but that's what we all use and that's what I would strongly suggest if you're going to patch Makefile.in. After all, it is trivial to install (in its own directory so it doesn't interfere with anything else).
I confess I'm not much interested in researching requirements for old versions -- I've "required" the latest released versions of all infrastructure stuff for texinfo (for people modifying infrastructure files) ever since I started maintaining it, and don't want to change. Anyway, what is this patch? Can we apply something so you don't have to? I was a bit surprised that aclocal is being run if you only patched Makefile.in, since that is autoconf, not automake. But I guess that's what aclocal does. Sorry, Karl
