Autoconf/automake build system.

This pull request contains an autoconf/automake build system.  This simplifies things and keeps from having to maintain makefiles for the wide range of systems that are already adequately supported by GNU autoconf and automake.  It also makes it easier for distribution maintainers to include this package in their distributions.

Also included is an autogen.sh script to kickstart the build system from git, and several minor corrections to the code to remove compiler warnings and get make CFLAGS="-O2 -Wall -D_FORTIFY_SOURCE=2 -Werror" to build clean.