Support in-place upgrades of new minio binary and releases. (#4961)

This PR allows 'minio update' to not only shows update banner
but also allows for in-place upgrades.

Updates are done safely by validating the downloaded
sha256 of the binary.

Fixes #4781

vendor/github.com/inconshreveable/go-update/hide_windows.go

@@ -0,0 +1,19 @@
+package update
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+func hideFile(path string) error {
+	kernel32 := syscall.NewLazyDLL("kernel32.dll")
+	setFileAttributes := kernel32.NewProc("SetFileAttributesW")
+
+	r1, _, err := setFileAttributes.Call(uintptr(unsafe.Pointer(syscall.StringToUTF16Ptr(path))), 2)
+
+	if r1 == 0 {
+		return err
+	} else {
+		return nil
+	}
+}