Many changes for wxInputHandler creation mainly related to:

Many changes for wxInputHandler creation mainly related to:

1. Allow the theme to create only the input handlers it customizes instead
   of forcing it to always create a handler even if the standard one is used:
   wxTheme::GetInputHandler() now takes wxInputConsumer to make this possible

2. Prefer delegation to inheritance when creating customized input handlers,
   almost all (except for wxStdScrollbarInputHandler) standard handler classes
   are now private, use wxClassName::GetStdInputHandler() to retrieve the
   standard handler for any class or polymorphic DoGetStdInputHandler()

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@41227 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775