Wrap label if necessary in wxInfoBar in wxGTK

Also update the sample to test showing an overlong message in wxInfoBar.

Closes https://github.com/wxWidgets/wxWidgets/pull/1443

See #14121.

src/gtk/infobar.cpp

@@ -196,7 +196,11 @@ void wxInfoBar::ShowMessage(const wxString& msg, int flags)
     if ( wxGTKImpl::ConvertMessageTypeFromWX(flags, &type) )
         gtk_info_bar_set_message_type(GTK_INFO_BAR(m_widget), type);
     gtk_label_set_text(GTK_LABEL(m_impl->m_label), wxGTK_CONV(msg));
-
+    gtk_label_set_line_wrap(GTK_LABEL(m_impl->m_label), TRUE );
+#if GTK_CHECK_VERSION(2,10,0)
+    if( wx_is_at_least_gtk2( 10 ) )
+        gtk_label_set_line_wrap_mode(GTK_LABEL(m_impl->m_label), PANGO_WRAP_WORD);
+#endif
     if ( !IsShown() )
         Show();