Man pages for automake and aclocal.

Man pages for automake and aclocal.

* configure.ac (HELP2MAN): New substitution.
* doc/Makefile.am (dist_man1_MANS, MAINTAINERCLEANFILES)
(update_mans): New macros.
($(srcdir)/aclocal-$(APIVERSION).1)
($(srcdir)/automake-$(APIVERSION).1): New rules, generate
man pages from the command line help with help2man.
($(srcdir)/aclocal.1, $(srcdir)/automake.1): New rules, for
`.so' man page links to the versioned pages.
* NEWS: Update.

Signed-off-by: Ralf Wildenhues <Ralf.Wildenhues@gmx.de>