add option to print the first line of an AST (for test output)

Parser/spec/ASTPrinting.jadd

@@ -91,4 +91,14 @@ aspect Debug {
         }
         return b;
     }
-}
\ No newline at end of file
+
+    protected String ASTNode.getPrettyPrintLine() {
+        PrettyPrinter sw = new PrettyPrinter("  ", false);
+        try {
+            this.prettyPrint(sw);
+            return sw.toString().trim().split("\n")[0];
+        } catch (RuntimeException e) {
+            return e.getMessage();
+        }
+    }
+}