misc/cgo/test: rewrite windows version of mysleep

Latest version of gcc (tdm-1) 5.1.0 refuses to compile our code
on windows/386 (see issue for details). Rewrite the code.

Fixes #14328

Change-Id: I70f4f063282bd2958cd2175f3974369dd49dd8dc
Reviewed-on: https://go-review.googlesource.com/20008Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

misc/cgo/test/callback_c.c

@@ -36,7 +36,7 @@ IntoC(void)
 long long
 mysleep(int seconds) {
 	long long st = GetTickCount();
-	sleep(seconds);
+	Sleep(1000 * seconds);
 	return st;
 }
 #else

misc/cgo/test/sleep_windows_386.go

-// Copyright 2011 The Go Authors.  All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package cgotest
-
-/*
-// mingw32 on windows/386 provides usleep() but not sleep(),
-// as we don't want to require all other OSes to provide usleep,
-// we emulate sleep(int s) using win32 API Sleep(int ms).
-
-#include <windows.h>
-
-unsigned int sleep(unsigned int seconds) {
-	Sleep(1000 * seconds);
-	return 0;
-}
-
-*/
-import "C"