configure.ac and Makefile.am rewrite

Sources used:
http://www.gnu.org/software/automake/manual/automake.html
https://www.flameeyes.eu/autotools-mythbuster/

subs.c includes config.h to get HAVE_PANGO

Rename INSTALL to BUILD.

Remove all autogenerated files.

The INSTALL file will be managed by autotools.

Add a smoke test.

Rename Changes to ChangeLog per GNU standards

Add AUTHORS, COPYING and NEWS

Set version to 8.2.1

DEFAULT_FDIR is no longer necessary because --datadir can be used instead, and
.fmt files will be put in the ${pkgdatadir}/abcm2ps directory.

Remove the custom text about building on unix

The generic INSTALL file is sufficient.

Remove Makefile.in which was rewritten to Makefile.am