Firebird bug CORE-5452 is fixed : Segfault when engine's dynamic library is unloaded right after closing worker threads

Firebird bug CORE-5452 is fixed http://tracker.firebirdsql.org/browse/CORE-5452

The issue was reported multiple times in Firebird devel list, I will mention here Damyan Ivanov (Debian) and Stephan Bergmann. (RedHat)

And related commit in Firebird 3.0 branch

https://github.com/FirebirdSQL/firebird/commit/40f782ae3e918c4f3842571ff8064be1c4f54961

Stephan Bergmann contributed the patch to LibreOffice in external/firebird