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, 10 insertions, 8 deletions

diff --git a/src/libstd/ffi/mod.rs b/src/libstd/ffi/mod.rs
index 28d9906eb93..72f7367c9dc 100644
--- a/src/libstd/ffi/mod.rs
+++ b/src/libstd/ffi/mod.rs
@@ -155,21 +155,23 @@
 
 #![stable(feature = "rust1", since = "1.0.0")]
 
-#[stable(feature = "rust1", since = "1.0.0")]
-pub use self::c_str::{CString, CStr, NulError, IntoStringError};
 #[stable(feature = "cstr_from_bytes", since = "1.10.0")]
-pub use self::c_str::{FromBytesWithNulError};
+pub use self::c_str::FromBytesWithNulError;
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use self::c_str::{CStr, CString, IntoStringError, NulError};
 
 #[stable(feature = "rust1", since = "1.0.0")]
-pub use self::os_str::{OsString, OsStr};
+pub use self::os_str::{OsStr, OsString};
 
 #[stable(feature = "core_c_void", since = "1.30.0")]
 pub use core::ffi::c_void;
 
-#[unstable(feature = "c_variadic",
-           reason = "the `c_variadic` feature has not been properly tested on \
-                     all supported platforms",
-           issue = "44930")]
+#[unstable(
+    feature = "c_variadic",
+    reason = "the `c_variadic` feature has not been properly tested on \
+              all supported platforms",
+    issue = "44930"
+)]
 pub use core::ffi::{VaList, VaListImpl};
 
 mod c_str;