Changes since the previous stable release:
- validate UTF-8 encoding of client version strings from peers
- don't time out tracker announces as eagerly while resolving hostnames
- fix NAT-PMP shutdown issue
- improve hostname lookup by merging identical lookups
- fix network route enumeration for large routing tables
- fixed issue where pop_alerts() could return old, invalid alerts
- fix issue when receiving have-all message before the metadata
- don't leave lingering part files handles open
- disallow calling add_piece() during checking
- fix incorrect filename truncation at multi-byte character
- always announce listen port 1 when using a proxy