LU-4975 ofd: documenting the ofd_trans.c

Fix up GPL header block to reference proper GPLv2 license URL.
Remove mention of contacting Sun, since they don't exist anymore.
Add introductory comment block for the ofd_trans.c file and add
function comment blocks to all functions in it.

Signed-off-by: Mikhail Pershin <mike.pershin@intel.com>
Change-Id: I3064afb8574f92c093efaa2bcc3178b33d15932d
Reviewed-on: http://review.whamcloud.com/10852
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Ned Bass <bass6@llnl.gov>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>