It crashes under valgrind, causing a valgrind error: valgrind gives us a
backtrace anyway, so we don't need it.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Also, we split the more sophisticated json_add helpers to avoid pulling in
everything into lightning-cli, and unify the routines to print struct
short_channel_id (it's ':', not '/' too).
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
