Add automake and autoconf for portable builds.

This change adds full autoconf/automake support so that the build is just ./configure;make;make install, and the creation of a tarball from a tag is just "make dist". It also includes and RPM spec file, so that RPM is just rpmbuild -tb sscep-version.tar.bz2.

A small detail - the configure.ac file contains the current version number of the code, this will need to be set to whatever the intended next version number is.