We no longer need a 'sendpay_result' structure, we can pass
appropriate parameter directly now they're simple calls.
Every waitsendpay command ends in tell_waiters_failed or
tell_waiters_success, which call sendpay_success or sendpay_fail on
all matching waiters. These all return 'struct command_result *'.
In cases where the result is immediately known, we call
sendpay_success/sendpay_fail directly for the command.
This also adds a helpful 'failcodename' field to the JSON output.
[ This was four separate cleanup patches, but that contained much
redundancy and was even worse to review ]
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
4e6b8e13a4