Re: improve named part/attachment detection

[ashiire <ashiire@users.noreply.github.com>]

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New comment by ashiire on mblaze repository

https://github.com/leahneukirchen/mblaze/pull/232#issuecomment-1426997809

Comment:
Fabricated example of the behavior in question.

```
$ ls mail_s_poezii.txt | mshow -t
mail_s_poezii.txt
  1: multipart/mixed size=825
    2: text/plain size=30
    3: text/plain size=53 name="kocka_leze_dirou.txt"
    4: text/plain size=98
$ ls mail_s_poezii.txt | mshow-patched -t
mail_s_poezii.txt
  1: multipart/mixed size=825
    2: text/plain size=30
    3: text/plain size=53 name="kocka_leze_dirou.txt"
    4: text/plain size=98 name="za_pravdu_je_ruzna_sazba.txt"
```

file contents:
```
From: Petr Klic <p.klic@example.com>
To: <umeni@example.com>
Subject: Poezie
Date: Wed, 14 Oct 2020 12:18:08 +0200
Message-ID: <setrise3750@example.com>
MIME-Version: 1.0
Content-Type: multipart/mixed;
        boundary="----=_NextPart_000_00DE_01D6A2E8.A7446C80"
Content-Language: cs

This is a multipart message in MIME format.

------=_NextPart_000_00DE_01D6A2E8.A7446C80
Content-Type: text/plain;
        charset="UTF-8"
Content-Transfer-Encoding: 8bit


Dobry den,

posilam poezii.


------=_NextPart_000_00DE_01D6A2E8.A7446C80
Content-Type: text/plain;
        charset="UTF-8";
        name="kocka_leze_dirou.txt"
Content-Transfer-Encoding: quoted-printable
Content-Disposition: attachment;
        filename="kocka_leze_dirou.txt"

kocka leze dirou
pes oknem
nebude-li prset
nezmoknem

------=_NextPart_000_00DE_01D6A2E8.A7446C80
Content-Type: text/plain;
        charset="UTF-8";
        name="za_pravdu_je_ruzna_sazba.txt"
Content-Transfer-Encoding: quoted-printable
Content-Disposition: attachment

za pravdu je ruzna sazba
nekdy pomnik
jindy vazba
kdo ji rika driv nez vcas
tomu pravda
zlame vaz

------=_NextPart_000_00DE_01D6A2E8.A7446C80--
```