Add links to research papers

[jeshan]

Hello Markus,
Some links for your research papers are missing from the home page and I'm adding here because I don't know of any better place to send you:

• Better Termination for Prolog with Constraints (pdf via Arxiv)
• Tor: extensible search with hookable disjunction (link was broken) (pdf via Semantic Scholar)
• Constraint solving for high-level WCET analysis (pdf via Arxiv)
• A generalised finite domain constraint solver for SWI-Prolog (pdf via Semantic Scholar)
• Declarative Language Extensions for Prolog Courses (pdf)
• Compiler Technology for Blue Gene Systems (pdf via Semantic Scholar)

Big fan,
Jeshan