MODIFIED: Splitted extend_arg_pos/7 in extend_arg_pos/6 and remove_arg_pos/7, to
	  improve readability, and to remove the need of extend_arg_pos_/7.

	  In remove_arg_pos/7, Passing the list of arguments of the call
	  obtained before the goal expansion, to avoid the need of subtract the
	  extra arguments at the end (subtract_eq/3).

	  Undo changes in dcg.pl to make positions in term_position/5
	  ground. they where not matching the term layout.

	  Separated special clause of expand_meta_arg/9 for N==0 to improve
	  readability and performance.

	  Added wrap_meta_pos/2 to preserve partial term position information
	  in the wrapped call.