No lower/upper case matching in search excerpt with international characters

Thanks for reporting this issue!
I could have sworn there already was an issue for this, but it seems I was mistaken, since I can't find it anymore. (There was, however, one for Drupal 7, which I had overlooked and found this way, so even better: #2889989: Multi-byte partial-match highlighting is not case-insensitive.)

The attached patch should fix this, please test!

PS: It seems you (like many others – it's really easy to misinterpret) are confused by the "Issue tags" field. As the guidelines state, they aren't meant for free text tags related to the issue, but only for specific categorization purposes, usually by module maintainers.
So, if you aren't sure your current usage is correct, please just leave the field empty.

Good to hear, thanks a lot for testing and reporting back!
Committed.

Oops, seems this isn't working on PHP 5.

Oops again.

Hm, maybe the Drupal test bot comes without multi-byte support in its PHP 5 environment?
In any case, it makes sense that we only test this if we expect it to be working – if MB support isn't available in PHP, that's not the fault of our module (I'd say).

Ah, I think I've got it. PHP 5.6 apparently changed the default encoding type to UTF-8, for earlier versions you need to specify it explicitly when calling mb_stripos() (and similar functions).

Committed.