btlazy2 : optimization for dictionary compression

we want the dictionary table to be fully sorted,
not just lazily filled.
Dictionary loading is a bit more intensive,
but it saves cpu cycles for match search during compression.

tests/playTests.sh

@@ -322,9 +322,14 @@ $ECHO "- Create first dictionary "
 TESTFILE=../programs/zstdcli.c
 $ZSTD --train *.c ../programs/*.c -o tmpDict
 cp $TESTFILE tmp
+$ECHO "- Dictionary compression roundtrip"
 $ZSTD -f tmp -D tmpDict
 $ZSTD -d tmp.zst -D tmpDict -fo result
 $DIFF $TESTFILE result
+$ECHO "- Dictionary compression with btlazy2 strategy"
+$ZSTD -f tmp -D tmpDict --zstd=strategy=6
+$ZSTD -d tmp.zst -D tmpDict -fo result
+$DIFF $TESTFILE result
 if [ -n "$hasMT" ]
 then
     $ECHO "- Test dictionary compression with multithreading "