Make hack for button creation in wxOSX more robust.

Don't crash when creating a plain wxButton with wxBU_NOTEXT style. This
happened because we skipped creating the peer (real implementation) in this
case entirely on the assumption that we were creating a wxBitmapButton, but
this is not necessarily the case. So now test that the creation of the peer is
really disabled before skipping it (this required adding ShouldCreatePeer()
accessor).

Merging wxWidgetImpl::CreateButton() and CreateBitmapButton() (and the same
thing for toggle buttons) would still be a better solution but while it's
trivial to do for Cocoa, it isn't for Carbon. And we can't use a single
function for Cocoa but different functions for Carbon, so for now just
continue to use this hack.

Closes #13622.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@72896 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/osx/window.h

@@ -259,7 +259,10 @@ public:
     // optimization to avoid creating a user pane in wxWindow::Create if we already know
     // we will replace it with our own peer
     void                DontCreatePeer();
-    
+
+    // return true unless DontCreatePeer() had been called
+    bool                ShouldCreatePeer() const;
+
     // sets the native implementation wrapper, can replace an existing peer, use peer = NULL to 
     // release existing peer
     void                SetPeer(wxOSXWidgetImpl* peer);