Replace deprecated MultiTerm add() method from RWK parser

Change-Id: I6c198488bc092aa60793bc8bb82b2b48dfdfd76f
diff --git a/lib/KorAP/XML/Annotation/RWK/Structure.pm b/lib/KorAP/XML/Annotation/RWK/Structure.pm
index 18edae7..1173d13 100644
--- a/lib/KorAP/XML/Annotation/RWK/Structure.pm
+++ b/lib/KorAP/XML/Annotation/RWK/Structure.pm
@@ -80,14 +80,12 @@
       }
 
       # Add the base sentence
-      my $mt = $mtt->add(
-        term    => '<>:base/s:' . $type,
-        o_start => $o_start,
-        o_end   => $_->[1],
-        p_start => $p_start,
-        p_end   => $_->[0],
-        pti     => 64
-      );
+      my $mt = $mtt->add_by_term('<>:base/s:' . $type);
+      $mt->set_o_start($o_start);
+      $mt->set_o_end($_->[1]);
+      $mt->set_p_start($p_start);
+      $mt->set_p_end($_->[0]);
+      $mt->set_pti(64);
       $mt->set_payload('<b>1');
 
       if ($type eq 's') {