Add the HandleConfigure module

Add the HandleConfigure module

This module handles the configure.ac files on the Automake side.  It required
to modify a bit the scan_autoconf_[file|traces] functions so we can pass them
the environment var for autoconf as arguments from the main file (otherwise it
wouldn't work).

* lib/Automake/HandleConfigure.pm: Module for handling configure.ac for automake.
* lib/Automake/Utils.pm: Add some necessary functions for the new
  HandleConfigure module.