[autoconf-conversion] Updating top-level files for automake

[Bonzini]

install.sh looks safe.

missing is backwards compatible (automake 1.7 invokes with --run, older automakes did
not).

> +    echo 1>&2 "\
> +WARNING: \`$1' is needed, and you do not seem to have it handy on your
> +         system.  You might have modified some files without having the
> +         proper tools for further handling them.
> +         You can get \`$1Help2man' as part of \`Autoconf' from any GNU

This is a typo BTW.

mkinstalldirs was practically rewritten, a context diff would be better but it looks
safe.

Paolo