Switched to the GNU Build System

Using a custum build system is not portable and it does not have all features
that required the [GNU Coding Standards][0].

In order to come as close as possible to the [GNU Coding Standards][0]. Using
[autotools][1] is a good practice.

There are some changes:

* the python library of this package is private so it does not install under
  the standard python `site-package` directory but on `pkglibdir`
  (default: `/usr/local/lib/cyg-apt`)

* to build from source it requires the `automake` package

* the build process command line:

  Before:

      $ make

  After:

      $ autoreconf -i && ./configure && make

* the tests suite command line:

  Before:

      $ make test

  After:

      $ make check

* the installation tests suite command line:

  Before:

      $ make installtest

  After:

      $ make installcheck

[0]: http://www.gnu.org/prep/standards/standards.html#Makefile-Conventions
[1]: http://www.gnu.org/software/automake/manual/automake.html#Autotools-Introduction