structeq() is too dangerous: if a structure has padding, it can fail
silently.
The new ccan/structeq instead provides a macro to define foo_eq(),
which does the right thing in case of padding (which none of our
structures currently have anyway).
Upgrade ccan, and use it everywhere. Except run-peer-wire.c, which
is only testing code and can use raw memcmp(): valgrind will tell us
if padding exists.
Interestingly, we still declared short_channel_id_eq, even though
we didn't define it any more!
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
