m4 error in bootstrap

[Francesco Potorti`]

I am doing a `make bootstrap' of the TEMACS_21_1_RC branch.  I get this
as the very first lines:

cd ~/gnu/emacs-pretest/
make -k bootstrap
cd /home/pot/gnu/emacs-pretest && autoconf
aclocal.m4:30: error: m4_defn: undefined macro: _m4_divert_diversion
autoconf/c.m4:801: AC_PROG_CC_STDC is expanded from...
aclocal.m4:30: the top level
make: *** [/home/pot/gnu/emacs-pretest/configure] Error 1
make: Failed to remake makefile `Makefile'.