Change the method of construction from:
So that a later patch can implement:
std::unordered_map<const DWARFUnit *, DWARFUnit::ScopedExtractDIEs> .emplace(DWARFUnit *,DWARFUnit *)
so that if the map element already exists DWARFUnit::ScopedExtractDIEs is not temporarily constructed. If the caller called DWARFUnit::ExtractDIEsScoped() as an emplace parameter it would get constructed already in the caller.
Patch also contains what I considered as a general cleanup.
All DWZ patches are also applied in: git clone -b dwz git://git.jankratochvil.net/lldb