Use wxObjCID instead of "struct objc_object*" to fix clang build.

Clang doesn't accept "struct objc_object*" as synonym for "id" in Objective-C
code, so use the real "id" for it while still using the struct pointer for C++
code where "id" is not defined.

Closes #13565.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@71517 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/osx/webviewhistoryitem_webkit.h

@@ -15,6 +15,8 @@
 #if wxUSE_WEBVIEW && wxUSE_WEBVIEW_WEBKIT && (defined(__WXOSX_COCOA__) \
                                           ||  defined(__WXOSX_CARBON__))
 
+#include "wx/osx/private/objcid.h"
+
 class WXDLLIMPEXP_WEBVIEW wxWebViewHistoryItem
 {
 public:
@@ -27,7 +29,7 @@ public:
 
 private:
     wxString m_url, m_title;
-    struct objc_object *m_histItem;
+    wxObjCID m_histItem;
 };
 
 #endif // wxUSE_WEBVIEW && wxUSE_WEBVIEW_WEBKIT