Add unittests target to the binary distribution (issue #1632)

- Move all tests from the top-level directory to tests/.
- Move files shared by cefclient and unittests to tests/shared/.
- Add a fused (single header/source file) version of gtest in
  tests/gtest/ with associated CMake configuration.
- Test-only headers are now exposed in include/test/. Unit test
  targets must define UNIT_TEST in order to access them.
- Replace usage of USING_CEF_SHARED with WRAPPING_CEF_SHARED for
  clarity (only the libcef_dll_wrapper target should define it).
- Remove the RENAME_DIRECTORY CMake macro which is no longer used.
- Remove C++11 usage from unittests sources for compatibility with
  the binary distribution configuration.
- Windows: Fix build errors due to chrome_elf.dll and imm32.lib
  missing from the CMake configuration.

tests/shared/browser/main_message_loop.cc

@@ -0,0 +1,37 @@
+// Copyright (c) 2015 The Chromium Embedded Framework Authors. All rights
+// reserved. Use of this source code is governed by a BSD-style license that
+// can be found in the LICENSE file.
+
+#include "tests/shared/browser/main_message_loop.h"
+
+#include "include/cef_task.h"
+#include "include/wrapper/cef_closure_task.h"
+
+namespace client {
+
+namespace {
+
+MainMessageLoop* g_main_message_loop = NULL;
+
+}  // namespace
+
+MainMessageLoop::MainMessageLoop() {
+  DCHECK(!g_main_message_loop);
+  g_main_message_loop = this;
+}
+
+MainMessageLoop::~MainMessageLoop() {
+  g_main_message_loop = NULL;
+}
+
+// static
+MainMessageLoop* MainMessageLoop::Get() {
+  DCHECK(g_main_message_loop);
+  return g_main_message_loop;
+}
+
+void MainMessageLoop::PostClosure(const base::Closure& closure) {
+  PostTask(CefCreateClosureTask(closure));
+}
+
+}  // namespace client