* applying bugfixes for issues reported by Chris Jones:
- two data races with path and module bin size
- changed stopping variable to atomic (it was not an issue because update of this variable can be picked up later by another thread)
- wrong atomic_thread_fence (acquire instead of release)

* fixed issue with deleting files when using single-buffering
* cleanup of comments
use std::mutex and scoped lock for fmt_.monlock_
replace memory fence with acces to atomic bool
fixed previous commit, also replaced fence with atomic access in FRD source