Log Message:
Update swi-prolog* to 5.6.17.

The 5.6.x release consolidates the 5.5.x development stream started in 2004.
Highlights:
* UNICODE character set support
* Unbounded integer arithmetic and rational numbers
* New and faster CHR release
* Added clp(r) constraints over reals
* Many enhancements to the web and notably sematic web libraries
* Much more ...