Revision 658

This very short patch fixes nrv2b compression in lar.

It also fixes lzma compression in lar to fix the silent memory
corruption that was possible when files didn't compress well.

It adds some comments to both files and the file that calls them.

Signed-off-by: Myles Watson <mylesgw@gmail.com>
Acked-by: Stefan Reinauer <stepan@coresystems.de>