nAvgBytesPerSec is the better factor in the presence of ADPCM, MPEG3 and other wave formats.

The background on this is that some applications use OpenGL and DirectDraw/Direct3D on
the same thread, typically using OpenGL for rendering and DirectDraw to get
the amount of available video memory. This means that we might replace the
application's current GL context with one with a completely different state,
but also that our current GL context might not be what we think it is.

The idea here is that we can restore the thread's current GL context on
context_release() if it doesn't correspond to the current wined3d context on
context_acquire().

Use a binary search to find the parent of a storage object being deleted.
We currently use IEnumSTATSTGImpl to do a linear search, which is
unnecessary.