DScanner 0.12.1 stopped working

[Carsten Schlote]

HI together,

it seems that dscanner started to fail recently, and at work some 
of our CI pipelines stopped working. I would care less, if this 
would have happed at home. But at work this opens more questions 
about the usability of dlang - for whatever purpose. So any help 
to solve this issue asap would be appreciated.

Error output:
```
.dub/packages/dscanner-0.12.1/dscanner/src/dscanner/analysis/helpers.d(59,32): Error: none of the overloads of `this` are callable using argument types `(CAllocatorImpl!(Mallocator, Flag.no))`
...
```

Is there any information available, what is causing this problem 
and how to fix it?

It happens with the latest versions of DMD and LDC2. Also it 
breaks with GDC, but GDC is not up to date. It worked before, so 
I suspect some changes in packages DScanner depends on.