Adding @TruffleBoundary

Author: ppisl

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/modules/MarshalModuleBuiltins.java

@@ -97,6 +97,7 @@ abstract static class DumpsNode extends PythonBuiltinNode {
 
         private @Child MarshallerNode marshaller = MarshallerNode.create();
 
+        @TruffleBoundary
         private byte[] dump(Object o, int version) {
             ByteArrayOutputStream baos = new ByteArrayOutputStream();
             DataOutputStream buffer = new DataOutputStream(baos);