util/{Foreign,Static}FifoBuffer: use C++11 initializers

src/util/ForeignFifoBuffer.hxx

 /*
- * Copyright (C) 2003-2014 Max Kellermann <max.kellermann@gmail.com>
+ * Copyright (C) 2003-2017 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
@@ -57,15 +57,15 @@ public:
 	typedef typename Range::const_pointer_type const_pointer_type;
 
 protected:
-	size_type head, tail, capacity;
+	size_type head = 0, tail = 0, capacity;
 	T *data;
 
 public:
 	explicit constexpr ForeignFifoBuffer(std::nullptr_t n)
-		:head(0), tail(0), capacity(0), data(n) {}
+		:capacity(0), data(n) {}
 
 	constexpr ForeignFifoBuffer(T *_data, size_type _capacity)
-		:head(0), tail(0), capacity(_capacity), data(_data) {}
+		:capacity(_capacity), data(_data) {}
 
 	ForeignFifoBuffer(ForeignFifoBuffer &&src)
 		:head(src.head), tail(src.tail),

src/util/StaticFifoBuffer.hxx

 /*
- * Copyright (C) 2003-2014 Max Kellermann <max.kellermann@gmail.com>
+ * Copyright (C) 2003-2017 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
@@ -52,13 +52,10 @@ public:
 	typedef WritableBuffer<T> Range;
 
 protected:
-	size_type head, tail;
+	size_type head = 0, tail = 0;
 	T data[size];
 
 public:
-	constexpr
-	StaticFifoBuffer():head(0), tail(0) {}
-
 	void Shift() {
 		if (head == 0)
 			return;