Bug#915547: Use iso639-3.xml file

[Osamu Aoki <osamu@debian.org>]

control: forwarded -1 https://github.com/ibus/ibus/issues/2062

Looks like pull request https://github.com/ibus/ibus/pull/2061 is
already applied to fujiwara's https://github.com/fujiwarat/ibus  repo
for 1.5.20.

1cd52548 ("src: use iso 639-3 to have names for more languages", 2018-12-17)

He didn't apply it to https://github.com/ibus/ibus repo

Let's close this when ibus 1.5.20 is packaged for post-buster.

If Daniel think upstream patch needs to be backported, can you create
pull request on salsa?

  https://salsa.debian.org/debian/ibus

With rationale to patch it for Debian.

Regards,

Osamu