* dropped dependency on iconv
* deprecate set_file_hash() in torrent creator, as it's superseded by v2 torrents
* deprecate mutable access to info_section in torrent_info
* removed deprecated lazy_entry/lazy_bdecode
* stats_alert deprecated
* remove bittyrant choking algorithm
* update userdata in add_torrent_params to be type-safe and add to torrent_handle
* add ip_filter to session_params
* added support for wolfSSL for SHA-1 hash and HTTPS (no Torrents over SSL)
* requires OpenSSL minimum version 1.0.0 with SNI support
* deprecated save_state() and load_state() on session in favour of new
write_session_params() and read_session_params()
* added support for BitTorrent v2 (see docs/upgrade_to_2.0.html)
* create_torrent() pad_file_limit parameter removed
* create_torrent() merkle- and optimize-alignment flags removed
* merkle_tree removed from add_torrent_params
* announce_entry expose information per v1 and v2 info-hash announces
* deprecated sha1_hash info_hash members on torrent_removed_alert,
torrent_deleted_alert, torrent_delete_failed_alert and add_torrent_params
* undeprecate error_file_metadata for torrent errors related to its metadata
* remove support for adding a torrent under a UUID (used for previous RSS support)
* remove deprecated feature to add torrents by file:// URL
* remove deprecated feature to download .torrent file from URL
* requires boost >= 1.66 to build
* update networking API to networking TS compatible boost.asio
* overhauled disk I/O subsystem to use memory mapped files (where available)
* libtorrent now requires C++14 to build
* added support for GnuTLS for HTTPS and torrents over SSL
* fix issue where stop-when-ready would not close files
* uTP performance, fix packet loss when sending is stalled
* uTP performance, prevent premature timeouts/resends
* uTP performance, more lenient nagle's algorithm to always allow one outstanding undersized packet
* uTP performance, piggy-back held back undersized packet with ACKs
* uTP performance, don't send redundant deferred ACKs
* fix wanted_done/done accounting when force-rechecking
* expose userdata via torrent_handle (back-port from 2.0)
* fix renaming of filenames that are too long for the filesystem
* made UPnP and LSD code avoid using select_reactor (to work around an issue on windows in boost.asio < 1.80)