Handle internationalized quote headers

[emersion]

See e.g. https://lists.sr.ht/~emersion/soju-dev/patches/12002#%[email protected]%3E

Le 19/08/2020 à 23:56, Simon Ser a écrit :

[YerinAlexey]

Do we even need to rely on them in the first place?

[emersion]

We want to strip these, so we need some way to detect them.

[YerinAlexey]

Now I see, I thought it was required to be present