And, reluctantly, default to bitcoind style.
"It's wrong to be right too soon."
Suggested-by: @cdecker
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
The easiest way to do this is to play with the 'wallet_tx' semantics
and have 'amount' have meaning even when 'all_funds' is set.
Note that we change the string 'Cannot afford funding transaction' to
'Cannot afford transaction' as this code is also used for withdrawls.
Inspired-by: molz on #c-lightning
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>