std::io: Modify some ReadBuf method signatures to return `&mut Self`

This allows using `ReadBuf` in a builder-like style and to setup a `ReadBuf` and
pass it to `read_buf` in a single expression, e.g.,

```
// With this PR:
reader.read_buf(ReadBuf::uninit(buf).assume_init(init_len))?;

// Previously:
let mut buf = ReadBuf::uninit(buf);
buf.assume_init(init_len);
reader.read_buf(&mut buf)?;
```

Signed-off-by: Nick Cameron <nrc@ncameron.org>

0 files changed, 0 insertions, 0 deletions