This is a regression test to check that the 3 byte OffsetToAlpha field
at the beginning of VP6SWFALPHAVIDEOPACKET type VideoFrame tags is
correctly skipped when splitting the color and alpha frame data.
Otherwise, the decoder errors out with "ShortData", because the
color frame is truncated by 3 bytes.

The one-frame SWF was extracted under Creative Commons 3.0 BY-NC-SA
license from https://github.com/doctorpangloss/multics (Left Comp_2.flv)
Author: Benjamin S. Berman
