Dead lock when stopping acquisition

Now that we have fixed the issue with the pthread-win32 library, new issues unfortunately get uncovered...

Camera::_setStatus locks the m_cond.mutex() used to signal a change of status. Lima's condition variable use PTHREAD_MUTEX_NORMAL mutexes, aka not recursive, which means that a function calling _setStatus should not have previously locked the m_cond.mutex(). This happens at least in Camera::_stopAcq, but I think also in the _AcqThread.