regtest: run seektest on image sequences

Seeking on image sequences doesn't actually work, so this
test isn't very useful until that capability is added.

Originally committed as revision 22286 to svn://svn.ffmpeg.org/ffmpeg/trunk

tests/ref/seek/%02d.jpg.ref

@@ -1,4 +1,4 @@
-ret: 0         st: 0 flags:1 dts: 0.000000 pts: 0.000000 pos:     -1 size: 31763
+ret: 0         st: 0 flags:1 dts: 0.000000 pts: 0.000000 pos:     -1 size: 31351
 ret:-EINVAL    st:-1 flags:0  ts:-1.000000
 ret:-EINVAL    st:-1 flags:1  ts: 1.894167
 ret:-EINVAL    st: 0 flags:0  ts: 0.800000

tests/ref/seek/%02d.pcx.ref

@@ -1,4 +1,4 @@
-ret: 0         st: 0 flags:1 dts: 0.000000 pts: 0.000000 pos:     -1 size:364147
+ret: 0         st: 0 flags:1 dts: 0.000000 pts: 0.000000 pos:     -1 size:364047
 ret:-EINVAL    st:-1 flags:0  ts:-1.000000
 ret:-EINVAL    st:-1 flags:1  ts: 1.894167
 ret:-EINVAL    st: 0 flags:0  ts: 0.800000

tests/ref/seek/%02d.sgi.ref

@@ -1,4 +1,4 @@
-ret: 0         st: 0 flags:1 dts: 0.000000 pts: 0.000000 pos:     -1 size:308151
+ret: 0         st: 0 flags:1 dts: 0.000000 pts: 0.000000 pos:     -1 size:308336
 ret:-EINVAL    st:-1 flags:0  ts:-1.000000
 ret:-EINVAL    st:-1 flags:1  ts: 1.894167
 ret:-EINVAL    st: 0 flags:0  ts: 0.800000

tests/ref/seek/%02d.tiff.ref

@@ -1,4 +1,4 @@
-ret: 0         st: 0 flags:1 dts: 0.000000 pts: 0.000000 pos:     -1 size:307131
+ret: 0         st: 0 flags:1 dts: 0.000000 pts: 0.000000 pos:     -1 size:307124
 ret:-EINVAL    st:-1 flags:0  ts:-1.000000
 ret:-EINVAL    st:-1 flags:1  ts: 1.894167
 ret:-EINVAL    st: 0 flags:0  ts: 0.800000

tests/seek-regression.sh

@@ -14,9 +14,10 @@ refdir="$src_path/tests/ref/seek"
 datadir="tests/data"
 
 list=$(ls -1 $datadir/vsynth2/* $datadir/acodec/* $datadir/lavf/*)
+imgs=$(for i in $datadir/images/*; do echo "$i/%02d.${i##*/}"; done)
 err=0
 
-for i in $list ; do
+for i in $list $imgs; do
     base=$(basename $i)
     logfile="$datadir/$base.seek.regression"
     reffile="$refdir/$base.ref"