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_std.h

@@ -0,0 +1,35 @@
+// 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.
+
+#ifndef CEF_TESTS_SHARED_BROWSER_MAIN_MESSAGE_LOOP_STD_H_
+#define CEF_TESTS_SHARED_BROWSER_MAIN_MESSAGE_LOOP_STD_H_
+#pragma once
+
+#include "tests/shared/browser/main_message_loop.h"
+
+namespace client {
+
+// Represents the main message loop in the browser process. This implementation
+// is a light-weight wrapper around the Chromium UI thread.
+class MainMessageLoopStd : public MainMessageLoop {
+ public:
+  MainMessageLoopStd();
+
+  // MainMessageLoop methods.
+  int Run() OVERRIDE;
+  void Quit() OVERRIDE;
+  void PostTask(CefRefPtr<CefTask> task) OVERRIDE;
+  bool RunsTasksOnCurrentThread() const OVERRIDE;
+
+#if defined(OS_WIN)
+  void SetCurrentModelessDialog(HWND hWndDialog) OVERRIDE;
+#endif
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(MainMessageLoopStd);
+};
+
+}  // namespace client
+
+#endif  // CEF_TESTS_SHARED_BROWSER_MAIN_MESSAGE_LOOP_STD_H_