HttpUtil class for Http specific utilities

Motivation:
The HTTP specification defines specific request-targets in https://tools.ietf.org/html/rfc7230#section-5.3. Netty does not have a way to distinguish between these differnt types, and there is currently no obvious location where these types of methods would live.

Modifications:
- Add methods to distinguish request-targets as defined in https://tools.ietf.org/html/rfc7230#section-5.3

Result:
Common utitlity methods exist to inpsect request-targets.

codec-http/src/main/java/io/netty/handler/codec/http/HttpUtil.java

@@ -0,0 +1,45 @@
+/*
+ * Copyright 2015 The Netty Project
+ *
+ * The Netty Project licenses this file to you 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 io.netty.handler.codec.http;
+
+import java.net.URI;
+
+/**
+ * Utility methods useful in the HTTP context.
+ */
+public final class HttpUtil {
+    private HttpUtil() { }
+
+    /**
+     * Determine if a uri is in origin-form according to
+     * <a href="https://tools.ietf.org/html/rfc7230#section-5.3">rfc7230, 5.3</a>.
+     */
+    public static boolean isOriginForm(URI uri) {
+        return uri.getScheme() == null && uri.getSchemeSpecificPart() == null &&
+               uri.getHost() == null && uri.getAuthority() == null;
+    }
+
+    /**
+     * Determine if a uri is in asteric-form according to
+     * <a href="https://tools.ietf.org/html/rfc7230#section-5.3">rfc7230, 5.3</a>.
+     */
+    public static boolean isAsteriskForm(URI uri) {
+        return "*".equals(uri.getPath()) &&
+                uri.getScheme() == null && uri.getSchemeSpecificPart() == null &&
+                uri.getHost() == null && uri.getAuthority() == null && uri.getQuery() == null &&
+                uri.getFragment() == null;
+    }
+}