libfdt defined a new version of the flattened device tree format,
version 17. It is backwards compatible with version 16, just adding
an extra header field giving the size of the blob's structure blob.
This patch adds support to dtc allowing it to read and write version
17 blobs. It also makes version 17 the default output version for
blobs.
At the same time we change the code to consistently using decimal
numbers for versions. Previously we sometimes used 16 and sometimes
0x10 to refer to version 16.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>