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.cc

@@ -0,0 +1,38 @@
+// 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_std.h"
+
+#include "include/cef_app.h"
+
+namespace client {
+
+MainMessageLoopStd::MainMessageLoopStd() {
+}
+
+int MainMessageLoopStd::Run() {
+  CefRunMessageLoop();
+  return 0;
+}
+
+void MainMessageLoopStd::Quit() {
+  CefQuitMessageLoop();
+}
+
+void MainMessageLoopStd::PostTask(CefRefPtr<CefTask> task) {
+  CefPostTask(TID_UI, task);
+}
+
+bool MainMessageLoopStd::RunsTasksOnCurrentThread() const {
+  return CefCurrentlyOn(TID_UI);
+}
+
+#if defined(OS_WIN)
+void MainMessageLoopStd::SetCurrentModelessDialog(HWND hWndDialog) {
+  // Nothing to do here. The Chromium message loop implementation will
+  // internally route dialog messages.
+}
+#endif
+
+}  // namespace client