Place regression test output files in subdirs per family

[ffmpeg] / tests / ref / vsynth2 / ljpeg

554a4a6a5a9058c588f8bf2de405bc70 *./tests/data/vsynth2/ljpeg.avi
4766914 ./tests/data/vsynth2/ljpeg.avi
dde5895817ad9d219f79a52d0bdfb001 *./tests/data/ljpeg.vsynth2.out.yuv
stddev:    0.00 PSNR:999.99 bytes:  7603200/  7603200