Create autotools plumbing for SoftEther.

Add autoconf and automake capabilities to SoftEther so that it can be built
like this:

	# autoreconf --force --install
	# ./configure
	# make install prefix=/tmp/softether

All standard configure parameters are supported, plus:

	# ./configure --enable-debug

Autotools support makes porting, cross compiling, and optimization much easier.

These GNU autoconf-archive components are used for dependency checking:

  * ax_check_openssl.m4
  * ax_check_zlib.m4
  * ax_lib_readline.m4
  * ax_pthread.m4
  * ax_with_curses.m4

NB: http://www.gnu.org/software/autoconf-archive/