backtrace: avoid duplicate backtrace objects.

This happened in my tal_dump(), and I couldn't see how we ended up
with object having more than one "backtrace".  Adding asserts that we
never added a second backtrace didn't trigger.

Finally I wondered if we were tal_steal() backtraces, and sure enough
we do that blinding in one place: libwally wrapping.  So fix that.

Signed-off-by: Rusty Russell <[email protected]>

fetchinvoice: add developer option to send raw invoice_request.

This will be used for bootstrap.bolt12.org to provide a raw request API.

Signed-off-by: Rusty Russell <[email protected]>

Hopefully closer to the real release...

v0.9.2: Now with 0-of-N Multisig

v0.9.2rc2 - Release Candidate Two