Make ssl-authentication really optional.

By configuring in JSON ssl-authentication to true for backend it will turn
listening apache to SSL based authorisation system.

SSL authorisation on such entry point is obligatory.

In order to follow typical ERP5 configuration SSL_CLIENT_S_DN_CN will be
passed as REMOTE_USER to Zope backend.

ERP5 CA is used to validate certificates.

This reverts commit 240cf0de.

Related problem was fixed by zc.buildout update.

version up : Python 2.7.3rc1 including security fixes. enable ipv6 explicitly. use our own libexpat.

Makefile overrides LDFLAGS and SHARED_LDFLAGS environment variables, thus the
resulting shared library didn't have RPATH set and libssl as well as engines
ending up not using SlapOS libcrypto.