This patch adds Milan Zamazal's conversion script and
modifies the mkinfo script to build the info doc files
from the LaTeX sources. Currently, the mac, doc and
inst TeX files are not handled.
Explicitly checks for GNU Emacs 21.
This is probably not sufficient by itself for the info generation, and is
being done mostly to keep the style consistent with additional patches
that will be applied to Doc/Makefile.