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/unittests/navigation_unittest.cc

@@ -9,9 +9,9 @@
 #include "include/cef_callback.h"
 #include "include/cef_scheme.h"
 #include "include/wrapper/cef_closure_task.h"
-#include "testing/gtest/include/gtest/gtest.h"
-#include "tests/cefclient/browser/client_app_browser.h"
-#include "tests/cefclient/renderer/client_app_renderer.h"
+#include "tests/gtest/include/gtest/gtest.h"
+#include "tests/shared/browser/client_app_browser.h"
+#include "tests/shared/renderer/client_app_renderer.h"
 #include "tests/unittests/test_handler.h"
 #include "tests/unittests/test_util.h"
 
@@ -715,7 +715,6 @@ class HistoryDynamicIFramesNavTestHandler : public TestHandler {
     got_load_end_[nav_].yes();
 
     if(nav_ == 3) {
-      CefString url = browser->GetMainFrame()->GetURL();
       EXPECT_STREQ(url.ToString().c_str(), kDynIfrNav1);
       DestroyTest();
       return;