Data race condition in HunspellWorker due to the abort variable

It is possible that two threads can access the "abort" member variable in HunspellWorker at the same time, as reported by Intel Inspector 2016.

In the reported case:

• Thread_1 executes "void HunspellWorker::run()"
• Thread_2 executes "HunspellWorker::~HunspellWorker()"

As "abort" is of type bool, an unprotected access to a shared variable occurs.