Add script to check overall ber-test performance with different seeds.

Signed-off-by: Stefan Westerfeld <stefan@space.twc.de>

src/seed-test.sh

+MAX_SEED=$1
+P1="$2"
+P2="$3"
+shift 3
+echo "max seed      : $MAX_SEED"
+echo "ber-test args : $@"
+echo "left          : $P1"
+echo "right         : $P2"
+for seed in $(seq 0 $MAX_SEED)
+do
+  echo $(AWM_PARAMS="$P1 --seed $seed" ber-test.sh "$@") $(AWM_PARAMS="$P2 --seed $seed" ber-test.sh "$@")
+done | awk '{a += $1; b += $2; c += $3; d += $4; n++; } {printf ("%.5f %.5f     -     %.5f %.5f    -    (((%s)))\n", a/n, b/n, c/n, d/n, $0);}'