OS specific syscall.Stat_t use into separate file

The use of Stat_t in request-example.go is unix specific and broke the
Windows OS builds. This is the minimal change to fix that.

This fixes #157.

request-example.go

@@ -11,7 +11,6 @@ import (
 	"os"
 	"path/filepath"
 	"sync"
-	"syscall"
 	"time"
 )
 
@@ -187,7 +186,7 @@ func (f *memFile) Mode() os.FileMode {
 func (f *memFile) ModTime() time.Time { return f.modtime }
 func (f *memFile) IsDir() bool        { return f.isdir }
 func (f *memFile) Sys() interface{} {
-	return &syscall.Stat_t{Uid: 65534, Gid: 65534}
+	return fakeFileInfoSys()
 }
 
 // Read/Write

request-stub.go

@@ -0,0 +1,9 @@
+// +build !cgo,!plan9 windows android
+
+package sftp
+
+import "syscall"
+
+func fakeFileInfoSys() interface{} {
+	return &syscall.Stat_t{Uid: 65534, Gid: 65534}
+}

request-unix.go

@@ -0,0 +1,10 @@
+// +build darwin dragonfly freebsd !android,linux netbsd openbsd solaris
+// +build cgo
+
+package sftp
+
+import "syscall"
+
+func fakeFileInfoSys() interface{} {
+	return &syscall.Stat_t{Uid: 65534, Gid: 65534}
+}