bug#26980: 25.2; Freeze & redisplay_internal & macOS

[Robert Vojta]

It’s caused by unicode character number 9448 (ⓨ). In 99% of cases, ascent of 
this character is 16, descent is 4, thus the sum is 20 and it equals to desired 
mode line height (20). Works like a charm.

What troubles me is that sometimes the descent is 5. Sometimes means it’s 
totally random. For the whole week, it’s always 4, works. And boom, it’s 5 -> 
16 + 5 -> 21 -> 21 != 20 and never ending loop is here.

And to answer what I have in mode line - Powerline theme from Spacemacs 
https://github.com/TheBB/spaceline

R.