lzma: update to lzma sdk 9.20

Updated code taken from latest lzma sdk release 9.20 at
http://downloads.sourceforge.net/sevenzip/lzma920.tar.bz2



This generates quite a lot of checkpatch warnings, but I guess we
need to keep the code style as is to avoid a massive job each time we
update this.

Signed-off-by: Stefan Reinauer <reinauer@google.com>

Signed-off-by: Simon Glass <sjg@chromium.org>