Log Message:
libtorrent: updated to 0.15.2

0.15.2

Use C++17.
Basic padding file support.
Fix multifile handling.
Macos fixes.
Thread-safe / preparation for multi-threaded trackers.
Updated list of peer IDs.
Fix undefined behavior in extents::insert.
Don't free memory not allocated by getaddrinfo(3) with freeaddrinfo
Fix pthread_setname_np race condition in thread_base::event_loop
Fix invalid memory accesses on exit
Thread-safe DNS resolver
Option for enabling f/madvise random.