Move platform specific code to different files

node_windows.go

@@ -0,0 +1,19 @@
+package restic
+
+import "os"
+
+func (node *Node) fill_extra(path string, fi os.FileInfo) error {
+	return nil
+}
+
+func (node *Node) createDevAt(path string) error {
+	return nil
+}
+
+func (node *Node) createCharDevAt(path string) error {
+	return nil
+}
+
+func (node *Node) createFifoAt(path string) error {
+	return nil
+}