Move it closer to ccan/json_out, in preparation for using that as a
replacement.
In particular:
1. Add a 'quote' field in json_add_member.
2. json_add_member now always escapes if 'quote' is true.
3. json_member_direct is exposed to allow avoiding of escaping.
4. json_add_hex can use this, so no longer needs to be in json_stream.c.
5. We don't make JSON manually, but always use helpers.
6. We now flush the stream (wake reader) only when we close it, or mark
command as pending.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
7f75043ab2