wasapisink: Re-align device period if necessary
Sometimes the minimum period advertised by a card results in an unaligned buffer size error during initialization in exclusive mode. In that case, we can fetch the actual buffer size in frames and calculate the period from that. We can't do this pre-emptively because we can't call GetBufferSize till Initialize has been called at least once. https://bugzilla.gnome.org/show_bug.cgi?id=793289