net: add `ReadHalf::{poll,poll_peak}` (#2151)

The `&mut self` requirements for `TcpStream` methods ensure that there are at
most two tasks using the stream--one for reading and one for writing.

`TcpStream::split` allows two separate tasks to hold a reference to a single
`TcpStream`. `TcpStream::{peek,poll_peek}` only poll for read readiness, and
therefore are safe to use with a `ReadHalf`.

Instead of duplicating `TcpStream::poll_peek`, a private method is now used by
both `poll_peek` methods that uses the fact that only a `&TcpStream` is
required.

Closes #2136

0 files changed, 0 insertions, 0 deletions