Add 3rdparty to source package

Add 3rdparty to source package

The new 3rdparty libraries are not added to the autotools build system, so
that they appear in the source package. They cannot be compiled yet with
autotools (although this would make sense for cross compilation with mingw),
but adding configure support for enabling/disabling these like we do for
boost is a bit more work, so I did not do it for now. Nevertheless, the
three new Makefile.am are already prepared for compilation.