Minor fix: do not use streams in REngine

Author: steve-s

com.oracle.truffle.r.engine/src/com/oracle/truffle/r/engine/REngine.java

@@ -281,7 +281,10 @@ private List<RSyntaxNode> parseSource(Source source) throws ParseException {
     @Override
     public RExpression parse(Source source) throws ParseException {
         List<RSyntaxNode> list = parseSource(source);
-        Object[] data = list.stream().map(node -> RASTUtils.createLanguageElement(node)).toArray();
+        Object[] data = new Object[list.size()];
+        for (int i = 0; i < data.length; i++) {
+            data[i] = RASTUtils.createLanguageElement(list.get(i));
+        }
         return RDataFactory.createExpression(data);
     }