Listview receives notifications not only from built-in header control,
but also from custom or subclassed application controls, there is no
need to assert(0) on application input, printing a FIXME is the maximum
we can do on an unknown input.

Previewly monochrome bitmaps were being created by CreateCompatibleBitmap
because the hdc passed into that call came from CreateCompatibleDC which is
initialized with a single pixel monochrome bitmap.