Format libstd/sys with rustfmt

This commit applies rustfmt with rust-lang/rust's default settings to
files in src/libstd/sys *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/sys -name '*.rs' \
        | xargs rustfmt --edition=2018 --unstable-features --skip-children
    $ rg libstd/sys outstanding_files | xargs git checkout --

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

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/sys/windows/stack_overflow.rs

@@ -1,7 +1,7 @@
 #![cfg_attr(test, allow(dead_code))]
 
-use crate::sys_common::util::report_overflow;
 use crate::sys::c;
+use crate::sys_common::util::report_overflow;
 
 pub struct Handler;
 
@@ -18,8 +18,7 @@ impl Handler {
     }
 }
 
-extern "system" fn vectored_handler(ExceptionInfo: *mut c::EXCEPTION_POINTERS)
-                                    -> c::LONG {
+extern "system" fn vectored_handler(ExceptionInfo: *mut c::EXCEPTION_POINTERS) -> c::LONG {
     unsafe {
         let rec = &(*(*ExceptionInfo).ExceptionRecord);
         let code = rec.ExceptionCode;