Calling a menu item's SetBitmap can result in a stack overflow. This
occurs when setting a bitmap after the menu item has already been added to
the menu and while running under Vista (and later). Under those
circumstances [Do]SetBitmap will call GetHBitmapForMenu which itself calls
SetBitmap again.
Fix by adding a simple check for re-entry.
Regression since r76202.
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@76754 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775