Make print_hexl function write to stdout rather than using printerr

print_hexl() currently uses printerr, but is really only necessary
for local debugging and should simply write to stdout.
Also change it to print the description internally.
Wrap it and its use in #ifdef DEBUG.

Signed-off-by: Kevin Coffman <kwc@citi.umich.edu>
Signed-off-by: Neil Brown <neilb@suse.de>