Update to Yap 6.0.6

Highlights:

- configure system rewritten and simplified
- better emulation of SWI, especially of C-interface, allows:
  o port of SWI  packages: sgml and plunit work better, clib, RDF,
    zlib and http seem to be working well, semweb compiles
  o better integration with C: it is now possible to call YAP from JPL
    reliably (all tests in the demos/java directory succeed in Linux)
  o it is now possible to create a stream with SWI routines and use
    YAP IO (parser, writer) on it
  o pyswip: YAP now includes a version of the pyswip package for
    experimentation: all the demos seem to be work (YAP must be compiled
    as a dynamic library)
- compilation in Sun and NetBSD
- YAP can now handle very, very large terms in compiled clauses.
- several new builtins
- improve thread implementation, especially locking in IO routines and indexing
    o fix C thread interface
- fix odbc support in MYDDAS
- fix overflow in ==
- fix bad call to subsumes/2
- new version of trie library, developed by Theo and Ricardo

(asau)