Libtorrent

* add new torrent_file_with_hashes() which includes piece layers for
creating .torrent files
* add file_prio_alert, posted when file priorities are updated
* fix issue where set_piece_hashes() would not propagate file errors
* add missing python binding for event_t
* add work-around for systems without fseeko() (such as Android)
* add convenience header libtorrent/libtorrent.hpp
* increase default max_allowed_in_request_queue
* fix loading non-ascii filenames on windows with torrent_info constructor (2.0 regression)
* add std::hash<> specialization for info_hash_t
* fix integer overflow in hash_picker and properly restrict max file sizes in torrents
* strengthen SSRF mitigation for web seeds

* add v1() and v2() functions to torrent_info
* fix piece_layers() to work for single-piece files
* fix python binding regression in session constructor flags
* fix unaligned piece requests in mmap_storage
* improve client_data_t ergonomics
* fix issue with concurrent access to part files

* fix attribute in single-file v2 torrent creation
* fix padding for empty files in v2 torrent creation
* add function to ask a file_storage whether it's v2 or not
* fix mtime field when creating single-file v2 torrents
* fix performance regression in checking files
* disable use of SetFileValidData() by default (windows). A new setting
allows enabling it

* dropped depenency on iconv
* deprecate set_file_hash() in torrent creator, as it's superceded by v2 torrents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)

* fixed tracker connections spinning when hostname lookups stall
* fixed error in pkg-config file generation in Jamfile
* improve backwards compatibility with loading magnet link resume files
* fix bind-to-device for tracker announces and UPnP
* rename peer_tos setting to peer_dscp
* fix bdecode support for large strings (>= 100 MB)

* boost 1.80 upgrade
* openssl 1.1.1q upgrade
* gradle 7.5.1 upgrade
* libtorrent update to RC_1_2 b5873f23b40ef9054b2bd6a4db2a2d327a56d4b1
* android NDK r25b (LTS) update (from r23)
* lt:fix wanted_done/done accounting when force-rechecking
* lt:expose userdata via torrent_handle (back-port from 2.0)
* lt:fix renaming of filenames that are too long for the filesystem
* lt:made UPnP and LSD code avoid using select_reactor (to work around an issue on windows in boost.asio < 1.80)
* lt:fixed tracker connections spinning when hostname lookups stall
* lt:fixed error in pkg-config file generation in Jamfile
* lt:improve backwards compatibility with loading magnet link resume files
* lt:fix bind-to-device for tracker announces and UPnP
* lt:rename peer_tos setting to peer_dscp
* lt:fix bdecode support for large strings (>= 100 MB)