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

src/libstd/io/impls.rs

@@ -1,7 +1,8 @@
 use crate::cmp;
-use crate::io::{self, SeekFrom, Read, Initializer, Write, Seek, BufRead, Error, ErrorKind,
-        IoSliceMut, IoSlice};
 use crate::fmt;
+use crate::io::{
+    self, BufRead, Error, ErrorKind, Initializer, IoSlice, IoSliceMut, Read, Seek, SeekFrom, Write,
+};
 use crate::mem;
 
 // =============================================================================
@@ -42,7 +43,9 @@ impl<R: Read + ?Sized> Read for &mut R {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<W: Write + ?Sized> Write for &mut W {
     #[inline]
-    fn write(&mut self, buf: &[u8]) -> io::Result<usize> { (**self).write(buf) }
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        (**self).write(buf)
+    }
 
     #[inline]
     fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
@@ -50,7 +53,9 @@ impl<W: Write + ?Sized> Write for &mut W {
     }
 
     #[inline]
-    fn flush(&mut self) -> io::Result<()> { (**self).flush() }
+    fn flush(&mut self) -> io::Result<()> {
+        (**self).flush()
+    }
 
     #[inline]
     fn write_all(&mut self, buf: &[u8]) -> io::Result<()> {
@@ -65,15 +70,21 @@ impl<W: Write + ?Sized> Write for &mut W {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<S: Seek + ?Sized> Seek for &mut S {
     #[inline]
-    fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> { (**self).seek(pos) }
+    fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> {
+        (**self).seek(pos)
+    }
 }
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<B: BufRead + ?Sized> BufRead for &mut B {
     #[inline]
-    fn fill_buf(&mut self) -> io::Result<&[u8]> { (**self).fill_buf() }
+    fn fill_buf(&mut self) -> io::Result<&[u8]> {
+        (**self).fill_buf()
+    }
 
     #[inline]
-    fn consume(&mut self, amt: usize) { (**self).consume(amt) }
+    fn consume(&mut self, amt: usize) {
+        (**self).consume(amt)
+    }
 
     #[inline]
     fn read_until(&mut self, byte: u8, buf: &mut Vec<u8>) -> io::Result<usize> {
@@ -121,7 +132,9 @@ impl<R: Read + ?Sized> Read for Box<R> {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<W: Write + ?Sized> Write for Box<W> {
     #[inline]
-    fn write(&mut self, buf: &[u8]) -> io::Result<usize> { (**self).write(buf) }
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        (**self).write(buf)
+    }
 
     #[inline]
     fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
@@ -129,7 +142,9 @@ impl<W: Write + ?Sized> Write for Box<W> {
     }
 
     #[inline]
-    fn flush(&mut self) -> io::Result<()> { (**self).flush() }
+    fn flush(&mut self) -> io::Result<()> {
+        (**self).flush()
+    }
 
     #[inline]
     fn write_all(&mut self, buf: &[u8]) -> io::Result<()> {
@@ -144,15 +159,21 @@ impl<W: Write + ?Sized> Write for Box<W> {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<S: Seek + ?Sized> Seek for Box<S> {
     #[inline]
-    fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> { (**self).seek(pos) }
+    fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> {
+        (**self).seek(pos)
+    }
 }
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<B: BufRead + ?Sized> BufRead for Box<B> {
     #[inline]
-    fn fill_buf(&mut self) -> io::Result<&[u8]> { (**self).fill_buf() }
+    fn fill_buf(&mut self) -> io::Result<&[u8]> {
+        (**self).fill_buf()
+    }
 
     #[inline]
-    fn consume(&mut self, amt: usize) { (**self).consume(amt) }
+    fn consume(&mut self, amt: usize) {
+        (**self).consume(amt)
+    }
 
     #[inline]
     fn read_until(&mut self, byte: u8, buf: &mut Vec<u8>) -> io::Result<usize> {
@@ -227,8 +248,7 @@ impl Read for &[u8] {
     #[inline]
     fn read_exact(&mut self, buf: &mut [u8]) -> io::Result<()> {
         if buf.len() > self.len() {
-            return Err(Error::new(ErrorKind::UnexpectedEof,
-                                  "failed to fill whole buffer"));
+            return Err(Error::new(ErrorKind::UnexpectedEof, "failed to fill whole buffer"));
         }
         let (a, b) = self.split_at(buf.len());
 
@@ -257,10 +277,14 @@ impl Read for &[u8] {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl BufRead for &[u8] {
     #[inline]
-    fn fill_buf(&mut self) -> io::Result<&[u8]> { Ok(*self) }
+    fn fill_buf(&mut self) -> io::Result<&[u8]> {
+        Ok(*self)
+    }
 
     #[inline]
-    fn consume(&mut self, amt: usize) { *self = &self[amt..]; }
+    fn consume(&mut self, amt: usize) {
+        *self = &self[amt..];
+    }
 }
 
 /// Write is implemented for `&mut [u8]` by copying into the slice, overwriting
@@ -302,7 +326,9 @@ impl Write for &mut [u8] {
     }
 
     #[inline]
-    fn flush(&mut self) -> io::Result<()> { Ok(()) }
+    fn flush(&mut self) -> io::Result<()> {
+        Ok(())
+    }
 }
 
 /// Write is implemented for `Vec<u8>` by appending to the vector.
@@ -332,7 +358,9 @@ impl Write for Vec<u8> {
     }
 
     #[inline]
-    fn flush(&mut self) -> io::Result<()> { Ok(()) }
+    fn flush(&mut self) -> io::Result<()> {
+        Ok(())
+    }
 }
 
 #[cfg(test)]