add missing '#pragma once'

src/io/deflate_ostream.hpp

@@ -1,3 +1,5 @@
+#pragma once
+
 #include <iostream>
 #include <streambuf>
 #include <memory>

src/io/devices/StdfsDevice.hpp

@@ -1,3 +1,5 @@
+#pragma once
+
 #include "Device.hpp"
 
 namespace io {

src/io/memory_ostream.hpp

@@ -1,3 +1,5 @@
+#pragma once
+
 #include <iostream>
 #include <streambuf>
 #include <cstring>