This commit is an implementation of [RFC 1212][rfc] which tweaks the behavior of
the `str::lines` and `BufRead::lines` iterators. Both iterators now account for
`\r\n` sequences in addition to `\n`, allowing for less surprising behavior
across platforms (especially in the `BufRead` case). Splitting *only* on the
`\n` character can still be achieved with `split('\n')` in both cases.
The `str::lines_any` function is also now deprecated as `str::lines` is a
drop-in replacement for it.
[rfc]: https://github.com/rust-lang/rfcs/blob/master/text/1212-line-endings.mdCloses#28032
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