Tokio v0.2.23

Maintenance release.

Fixes

• time: report correct error for timers that exceed max duration (#2023)
• time: fix resetting expired timers causing panics (#2587)
• macros: silence unreachable_code warning in select! (#2678)
• rt: fix potential leak during runtime shutdown (#2649)
• sync: fix missing notification during mpsc close (#2854)

Changes

• io: always re-export std::io (#2606)
• dependencies: update parking_lot dependency to 0.11.0 (#2676)
• io: rewrite read_to_end and read_to_string (#2560)
• coop: reset coop budget when blocking in block_on (#2711)
• sync: better Debug for Mutex (#2725)
• net: make UnixListener::poll_accept public (#2880)
• dep: raise lazy_static to 1.4.0 (#3132)
• dep: raise slab to 0.4.2 (#3132)

Added

• io: add io::duplex() as bidirectional reader/writer (#2661)
• net: introduce split and into_split on UnixDatagram (#2557)
• net: ensure that unix sockets have both split and into_split (#2687)
• net: add try_recv/from & try_send/to to UnixDatagram (#1677)
• net: Add UdpSocket::{try_send,try_send_to} methods (#1979)
• net: implement ToSocketAddrs for (String, u16) (#2724)
• io: add ReaderStream (#2714)
• sync: implement map methods (#2771)