INT-4272: Read Only Header Improvements

JIRA: https://jira.spring.io/browse/INT-4272

- Honor read only header configuration when building from an unchanged message
- Support adding read only headers to the message builder factory

* Move `IntegrationMessageHeaderAccessor.containsReadOnly()` to the
`MessageBuilder` to avoid confusing

**Cherry-pick to 4.3.x**

spring-integration-core/src/test/java/org/springframework/integration/support/MessageBuilderTests.java

@@ -0,0 +1,50 @@
+/*
+ * Copyright 2017 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.integration.support;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertThat;
+
+import org.junit.Test;
+
+import org.springframework.messaging.Message;
+
+/**
+ * @author Gary Russell
+ * @since 4.3.10
+ *
+ */
+public class MessageBuilderTests {
+
+	@Test
+	public void testReadOnlyHeaders() {
+		DefaultMessageBuilderFactory factory = new DefaultMessageBuilderFactory();
+		Message<?> message = factory.withPayload("bar").setHeader("foo", "baz").setHeader("qux", "fiz").build();
+		assertThat(message.getHeaders().get("foo"), equalTo("baz"));
+		assertThat(message.getHeaders().get("qux"), equalTo("fiz"));
+		factory.setReadOnlyHeaders("foo");
+		message = factory.fromMessage(message).build();
+		assertNull(message.getHeaders().get("foo"));
+		assertThat(message.getHeaders().get("qux"), equalTo("fiz"));
+		factory.addReadOnlyHeaders("qux");
+		message = factory.fromMessage(message).build();
+		assertNull(message.getHeaders().get("foo"));
+		assertNull(message.getHeaders().get("qux"));
+	}
+
+}