Restore removed <algorithm> includes.

Turns out these were needed after all. For some reason, on Windows and
Mac, <algorithm> gets auto-included by something else so I don't notice
when it's missing, and MSVC's include dependency tracker doesn't see it
either.

Core/Dialog/PSPNpSigninDialog.cpp

@@ -15,9 +15,7 @@
 // Official git repository and contact information can be found at
 // https://github.com/hrydgard/ppsspp and http://www.ppsspp.org/.
 
-#if defined(_WIN32)
-#include "Common/CommonWindows.h"
-#endif
+#include <algorithm>
 #include "Common/TimeUtil.h"
 #include "Common/Data/Text/I18n.h"
 #include "Common/Serialize/Serializer.h"