I did a brief audit of tmpctx uses, and we do leak them in various
corner cases. Fortunely, all our daemons are based on some kind of
I/O loop, so it's fairly easy to clean a global tmpctx at that point.
This makes things a bit neater, and slightly more efficient, but also
clearer: I avoided creating a tmpctx in a few places because I didn't
want to add another allocation. With that penalty removed, I can use
it more freely and hopefully write clearer code.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
