mdump does not work on lz4 files

[dd1]

mdump does not recognize lz4 files, prints the usage instead:

‌

$ mdump -x run00721.mid.lz4
>>> data type (-t) should be set by hand in -x mode for tape <<< 
mdump for online  -l #            : display # events (look 1)
...

‌

[dd1]

fixed commit 9c88e8c000affc3fb381c174ba601394b6ebf032. K.O.