dd_rhelp THANKS file

dd_rhelp has originally been written by Valentin LAB.
dd_rescue has originally been written by Kurt Garloff.

 Many people further contributed to dd_rhelp by reporting problems,
suggesting various improvements or submitting actual code.
Here is a list of these people. Help me keep it complete and
exempt of errors.

Michael Lucas (for asking good questions)
Asheesh Laroia (help for the Darwin / Mac OS X support)
Pätrick Guillot (for reminding me the problem with my obsoletes head/tail arguments as others)

And big thanks to all those from which I've received mail !