Applied patch for wxComboBox and wxListBox to

  Applied patch for wxComboBox and wxListBox to
    prevent "hanging" in single selection mode.
    Also removed call to AddPendingEvent and
    changed wxLB_EXTENDED mode so that no changes
    to the listbox go unnoticed.
  I do wonder what the difference between multiple
    and extended list boxes actually are.
  Not suer what I changed in the other files.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@11310 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775