add minimal ctxtcall.h

[Rob Shearman]

2008/9/8 Louis. Lenders <xerox_xerox2000 at yahoo.co.uk>:
> +typedef HRESULT (*PFNCONTEXTCALL)(ComCallData *pparam);

You don't explicitly tell widl that this function is a __stdcall
function. Please check if that is automatically added in the generated
header file. If not, you'll have to specify it here.

> +
> +/*****************************************************************************
> + * IContextcallback interface
> + */

Please change "IContextcallback" to "IContextCallback".

-- 
Rob Shearman