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.

This makes sure that the flag is set correctly when
surface_allocate_surface is called and client storage is disabled
properly for converted surfaces.

Use plain xrender_blit for mono -> mono copies, masking in combination
with PictOpOver doesn't make sense and doesn't work.

Fixes a Valgrind warning.