boilerplate
(rasqal_rowsource_sv_header_callback): Strip ? from varname
Import raptor_ntriples.c

(rasqal_new_term_from_counted_string): Internal version of
GIT head raptor_new_term_from_counted_string taking a rasqal_world
instead.
Added rasqal_new_literal_from_term to hold term->literal code

(rasqal_new_literal_from_term): Added with proper error handling

(raptor_statement_as_rasqal_triple): Use above and now is trivial.