Integrate GNU automake and GNU libtool

Based on and including the autoconf cleanup in #22.

Replaces the hand-written Makefile.in files with automake configuration files, including the use of GNU libtool to generate static and shared libraries. All files that are generated or copied by automake have been removed from the repository and can be regenerated using ```autoreconf```.

These changes actually implement all make targets required by the GNU Coding Standards and expected by many users, like ```distclean```, ```dist``` and ```uninstall```, as well as VPATH builds and proper cross-compilation. This makes embedding within other autotools-based packages a lot easier.