Follow the standard way.
JIRA issue: CORE-19469
- Use STDMETHODIMP and override keyword
instead of virtual HRESULT STDMETHODCALLTYPE.
- Delete CTaskBand::ProcessMessage and
CTaskBand::ContainsWindow methods.
I think they are useless.
fixes CORE-18807 'Our explorer.exe ATL-asserts when executed on XPSP3'
which most likely got unhidden when we enabled the ATL-assertions in
0.4.15-dev-5023-g 55343f04b0
