Format libstd with rustfmt

This commit applies rustfmt with rust-lang/rust's default settings to
files in src/libstd *that are not involved in any currently open PR* to
minimize merge conflicts. THe list of files involved in open PRs was
determined by querying GitHub's GraphQL API with this script:
https://gist.github.com/dtolnay/aa9c34993dc051a4f344d1b10e4487e8

With the list of files from the script in outstanding_files, the
relevant commands were:

    $ find src/libstd -name '*.rs' \
        | xargs rustfmt --edition=2018 --unstable-features --skip-children
    $ rg libstd outstanding_files | xargs git checkout --

Repeating this process several months apart should get us coverage of
most of the rest of libstd.

To confirm no funny business:

    $ git checkout $THIS_COMMIT^
    $ git show --pretty= --name-only $THIS_COMMIT \
        | xargs rustfmt --edition=2018 --unstable-features --skip-children
    $ git diff $THIS_COMMIT  # there should be no difference

1 files changed, 6 insertions, 9 deletions

diff --git a/src/libstd/sys_common/os_str_bytes.rs b/src/libstd/sys_common/os_str_bytes.rs
index 3753269adfe..a2608ad4000 100644
--- a/src/libstd/sys_common/os_str_bytes.rs
+++ b/src/libstd/sys_common/os_str_bytes.rs
@@ -4,18 +4,18 @@
 use crate::borrow::Cow;
 use crate::ffi::{OsStr, OsString};
 use crate::fmt;
-use crate::str;
 use crate::mem;
 use crate::rc::Rc;
+use crate::str;
 use crate::sync::Arc;
-use crate::sys_common::{FromInner, IntoInner, AsInner};
 use crate::sys_common::bytestring::debug_fmt_bytestring;
+use crate::sys_common::{AsInner, FromInner, IntoInner};
 
 use core::str::lossy::Utf8Lossy;
 
 #[derive(Clone, Hash)]
 pub(crate) struct Buf {
-    pub inner: Vec<u8>
+    pub inner: Vec<u8>,
 }
 
 // FIXME:
@@ -25,7 +25,7 @@ pub(crate) struct Buf {
 // Anyway, `Slice` representation and layout are considered implementation detail, are
 // not documented and must not be relied upon.
 pub(crate) struct Slice {
-    pub inner: [u8]
+    pub inner: [u8],
 }
 
 impl fmt::Debug for Slice {
@@ -64,7 +64,6 @@ impl AsInner<[u8]> for Buf {
     }
 }
 
-
 impl Buf {
     pub fn from_string(s: String) -> Buf {
         Buf { inner: s.into_bytes() }
@@ -72,9 +71,7 @@ impl Buf {
 
     #[inline]
     pub fn with_capacity(capacity: usize) -> Buf {
-        Buf {
-            inner: Vec::with_capacity(capacity)
-        }
+        Buf { inner: Vec::with_capacity(capacity) }
     }
 
     #[inline]
@@ -112,7 +109,7 @@ impl Buf {
     }
 
     pub fn into_string(self) -> Result<String, Buf> {
-        String::from_utf8(self.inner).map_err(|p| Buf { inner: p.into_bytes() } )
+        String::from_utf8(self.inner).map_err(|p| Buf { inner: p.into_bytes() })
     }
 
     pub fn push_slice(&mut self, s: &Slice) {