Initialize wxButton::m_authNeeded in ctor and not Create() in wxMSW.

Ensure that the member is always initialized as calling GetAuthNeeded() for a
default-constructed button would access a non-initialized variable before.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@67058 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msw/button.cpp

@@ -450,8 +450,6 @@ bool wxButton::Create(wxWindow *parent,
                       const wxValidator& validator,
                       const wxString& name)
 {
-    m_authNeeded = false;
-
     wxString label(lbl);
     if (label.empty() && wxIsStockID(id))
     {