Update raptor to version 1.4.17

The main changes to this release are:
Added two new JSON serializers: resource-centric 'json' (Talis RDF/JSON)
and triple-centric 'json-triples'.
Made I/O Stream class raptor_iostream support reading as well as writing
with new constructors and new methods.
Added a new public SAX2 API class raptor_sax2 exposing the existing
internal API which has been around since the first release of Raptor 8
years ago and runs on top of either expat or libxml2.
Added new public error handlers structure raptor_error_handlers containing
a set of (function, data pointers) pairs called raptor_handler_closure for
each error log level. Added raptor_log_level enum for the error log level.
Added an initialization function for the structure,
raptor_error_handlers_init().
Several other API changes, fixes and improvements were made.

1.4.16 changes:
Provide 100% support for the GRDDL W3C Recommendation of 2007-09-11.
The Turtle parser and serializer were updated to support @base for
specifying a base URI, following Turtle of 2007-09-11.
The Turtle and RDF/XML serializers had performance improvements for large
graphs.
Added a TRiG Parser based on Turtle with named graph support.
Several other API changes, fixes and improvements were made.

(markd)