Use wxLogStatus() to update the status bar, this is shorter and simpler
than using GetStatusBar()->SetStatusText(wxString::Format(...)).
Also use wxFrame::SetStatusText() which forwards to wxStatusBar method
with the same name when we want to just clear the status bar.
No real changes.
Don't force the application code to deal with wxObjectDataPtr<> or,
worse, calling {Inc,Dec}Ref() manually by hiding it inside the wx
objects themselves and giving the value-like semantics to them.
There should be no real changes in the behaviour, but the API does
change significantly. Notably, wxWebRequest is not a wxEvtHandler itself
any longer, as this would be incompatible with the value semantics, and
an event handler needs to be specified when creating it, so that it
could be notified about the request state changes.
