Changes to header

[scootergrisen]

See: vim/vim#3040

[k-takata]

Please show a reference why <...> is preferred than (...).
I don't understand why you want to change Language-Team: to Japanese from vim-jp. Our team name is "vim-jp", not "Japanese".
Should Language: be two letter code? Can you show a reference?
Is "UTF-8" better than "utf-8"? I think "utf-8" is widely used and it works fine.

[scootergrisen]

Here is a pot file (http://translationproject.org/POT-files/a2ps-4.14.pot) with:

"Language-Team: LANGUAGE <LL@li.org>\n":

You can also compare with the other Vim po files. The ja*.po files seems to be the only one using (...).

https://www.gnu.org/software/gettext/manual/gettext.html#Header-Entry says:

Language-Team

Fill in the English name of the language, and the email address or homepage URL of the language team you are part of.

https://www.gnu.org/software/gettext/manual/gettext.html#Header-Entry says "UTF-8".

[k-takata]

It might be better to add a link to the original PR. I edited your comment.

You can also compare with the other Vim po files. The ja*.po files seems to be the only one using (...).

Only ja*.po are translated by a team and using a URL here. The others uses email addresses.
There's no obvious example using a URL, so I don't know if <URL> is preferred.
... But the <URL> notation is also used in Markdown and is popular, so this might be acceptable.

https://www.gnu.org/software/gettext/manual/gettext.html#Header-Entry says "UTF-8".

It also says that:

The character encoding name can be written in either upper or lower case. Usually upper case is preferred.

It is case insensitive, but "UTF-8" seems to be preferred.

Okay, your PR seems reasonable.
@koron Any thoughts?