Removed some bugs and improved exception handling code.
Replaced some `assert()`s by `CU_ASSERT_THROW()`s.
Improved code for `ConcurrentQeue`: The mutex will not be locked during possibly lengthy operations.
Implemented `Monitor<T>` wrapper class which provides a safe implementation of the monitor pattern.
Added member function withUniqueLock() to Monitor template class.
Reimplemented ConcurrentQueue in terms of the template class `Monitor`.