Fix clang style warnings in webrtc/base

Mostly this consists of marking functions with override when
applicable, and moving function bodies from .h to .cc files.

Not inlining virtual functions with simple bodies such as

  { return false; }

strikes me as probably losing more in readability than we gain in
binary size and compilation time, but I guess it's just like any other
case where enabling a generally good warning forces us to write
slightly worse code in a couple of places.

BUG=163
R=kjellander@webrtc.org, tommi@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/47429004

Cr-Commit-Position: refs/heads/master@{#8656}
git-svn-id: http://webrtc.googlecode.com/svn/trunk@8656 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/base/asyncpacketsocket.cc

@@ -0,0 +1,29 @@
+/*
+ *  Copyright 2015 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "webrtc/base/asyncpacketsocket.h"
+
+namespace rtc {
+
+PacketTimeUpdateParams::PacketTimeUpdateParams()
+    : rtp_sendtime_extension_id(-1),
+      srtp_auth_tag_len(-1),
+      srtp_packet_index(-1) {
+}
+
+PacketTimeUpdateParams::~PacketTimeUpdateParams() = default;
+
+AsyncPacketSocket::AsyncPacketSocket() {
+}
+
+AsyncPacketSocket::~AsyncPacketSocket() {
+}
+
+};  // namespace rtc