configure should check that install-info is on PATH

[Eric Hanchrow]

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In GNU Emacs 21.2.1 (i386-debian-linux-gnu, X toolkit, Xaw3d scroll bars)
 of 2002-03-22 on raven, modified by Debian
configured using `configure  i386-debian-linux-gnu --prefix=/usr 
--sharedstatedir=/var/lib --libexecdir=/usr/lib --localstatedir=/var/lib 
--infodir=/usr/share/info --mandir=/usr/share/man --with-pop=yes --with-x=yes 
--with-x-toolkit=athena --without-gif'

A number of times I've noticed that `make install' fails because
`install-info' is not on my PATH.  (On my GNU/Linux distro,
install-info is in /usr/sbin, which isn't on my path unless I'm root.)
It would be nice if configure could notice that, and warn me, or
better yet, append the needed directory to my PATH for the duration of
the `make'.