Fix CScriptID(const CScript& in) in empty script case

Previously an empty script wouldn't be hashed, and CScriptID would be
assigned the incorrect value of 0 instead. This bug can be seen in the
RPC decodescript command:

    $ btc decodescript ""
    {
        "asm" : "",
        "type" : "nonstandard",
        "p2sh" : "31h1vYVSYuKP6AhS86fbRdMw9XHieotbST"
    }

Correct output:

    $ btc decodescript ""
    {
        "asm" : "",
        "type" : "nonstandard",
        "p2sh" : "3J98t1WpEZ73CNmQviecrnyiWrnqRhWNLy"
    }

Rebased-From: d78f0dafd520f481f909cca7e361a4e482cbea72
Github-Pull: #5541
gitian: attempt to fix tarball determinisim

Rebased-From: 566c6cb8a2a277d9c5e4897ad02c5bb15786523c
Github-Pull: #5536
en: Avoid ambiguous language regarding when transactions confirm

Rebased-From: a15dba5dff1229b67ff44bf16ff14063e885f376
Github-Pull: #5533
Release notes: formatting, headers-first, rest