util/*FifoBuffer: use `using` instead of `typedef`

src/util/DynamicFifoBuffer.hxx

 /*
- * Copyright 2003-2018 Max Kellermann <max.kellermann@gmail.com>
+ * Copyright 2003-2019 Max Kellermann <max.kellermann@gmail.com>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -40,10 +40,10 @@
 template<typename T>
 class DynamicFifoBuffer : protected ForeignFifoBuffer<T> {
 public:
-	typedef typename ForeignFifoBuffer<T>::size_type size_type;
-	typedef typename ForeignFifoBuffer<T>::pointer_type pointer_type;
-	typedef typename ForeignFifoBuffer<T>::const_pointer_type const_pointer_type;
-	typedef typename ForeignFifoBuffer<T>::Range Range;
+	using typename ForeignFifoBuffer<T>::size_type;
+	using typename ForeignFifoBuffer<T>::pointer_type;
+	using typename ForeignFifoBuffer<T>::const_pointer_type;
+	using typename ForeignFifoBuffer<T>::Range;
 
 	explicit DynamicFifoBuffer(size_type _capacity) noexcept
 		:ForeignFifoBuffer<T>(new T[_capacity], _capacity) {}

src/util/ForeignFifoBuffer.hxx

 /*
- * Copyright (C) 2003-2017 Max Kellermann <max.kellermann@gmail.com>
+ * Copyright 2003-2019 Max Kellermann <max.kellermann@gmail.com>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -51,10 +51,10 @@
 template<typename T>
 class ForeignFifoBuffer {
 public:
-	typedef size_t size_type;
-	typedef WritableBuffer<T> Range;
-	typedef typename Range::pointer_type pointer_type;
-	typedef typename Range::const_pointer_type const_pointer_type;
+	using size_type = size_t;
+	using Range = WritableBuffer<T>;
+	using pointer_type = typename Range::pointer_type;
+	using const_pointer_type = typename Range::const_pointer_type;
 
 protected:
 	size_type head = 0, tail = 0, capacity;

src/util/StaticFifoBuffer.hxx

 /*
- * Copyright (C) 2003-2017 Max Kellermann <max.kellermann@gmail.com>
+ * Copyright 2003-2019 Max Kellermann <max.kellermann@gmail.com>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -46,10 +46,8 @@
 template<class T, size_t size>
 class StaticFifoBuffer {
 public:
-	typedef size_t size_type;
-
-public:
-	typedef WritableBuffer<T> Range;
+	using size_type = size_t;
+	using Range = WritableBuffer<T>;
 
 protected:
 	size_type head = 0, tail = 0;