Fix setting of active tab when frame process is 64-bit, but tab processes are 32-bit.

- the difference in bitness requires use of the HWNDX type.
- from what I can tell, the default behavior of Internet Explorer 11 is
  to run the frame process under 64-bit and the tab processes as 32-bit
  for compatibility with older plugins. If Enhanced Protection mode is
  enabled (which requires a restart), the tab processes run as 64-bit.
Fix forge.button.setIcon on IE.

- in FrameServer::ProxyListen, the currentToolbar variable (an index
  into FrameServer.m_buttons) was being set before the m_activeToolbar
  member was initialized (or modified) by the LoadCommand. The
  currentToolbar is now being set on every time through the channel
  command processing loop.
- Also, made button lookup by the toolbar a bit more robust by using
  hash_map.find instead of operator[]. operator[] will create an
  "empty" button when the toolbar is invalid/unset/etc and this was
  causing button_setIconCommand to either fail or set the icon for
  incorrect button (such as the Home button on IE 10 or 11).
Update IE native code.