"sphinx_add_hop" takes a literal hop to include,
"sphinx_add_modern_hop" prepends the length. Now we always prepend a
length, make it clear that the literal version is a shortcut:
* sphinx_add_hop -> sphinx_add_hop_has_length
* sphinx_add_modern_hop -> sphinx_add_hop
In addition, we check that length is actually correct! This means
`createonion` can no longer create legacy or otherwise-invalid onions:
fix tests and update man page to remove legacy usage.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Changed: JSON-RPC: `createonion` no longer allows non-TLV-style payloads.
Rusty Russell