I've committed the changes below to help give more hints about the need
to run libtoolize. I ended up adding a new section to the manual and
referring to it from the alpha-NEWS and variable warning. It's in the
below patch as the new
  @node Libtool library used but LIBTOOL is undefined

After making a hello,world using libtool (attached for my own memory :),
I found that just running aclocal -I... did not suffice.  After the
aclocal run, the next error was:
  configure.ac:9: error: required file './ltmain.sh' not found
just as already described in the manual (preceding node).  So running
libtoolize is needed, not just playing with -I options, as far as I can tell.

I also discovered that although libtoolize only asks you to "consider"
creating an m4/ subdir for macros, in fact it is a requirement, at least
in the case of automake and libtool in different prefixes.  Without
AC_CONFIG_MACRO_DIRS([m4]), the original
"error: Libtool library used but 'LIBTOOL' is undefined" persists.

(Aside: It was also rather irritating to have to run automake
--add-missing three separate times as new pieces were found. Oh well.)

It's all quite a confusing conglomeration, but I don't think there's
anything to do about here.

I guess I will leave this open in hopes of figuring out that m4 stub
approach, but this is all I can see to do for the 1.17 release.  (I've
got nothing else pending for 1.17, so if anyone knows of a reason to
delay, let me know asap.) --thanks, karl.