Merge remote-tracking branch 'upstream/master'

* upstream/master:
  Headers: emplace_{front,back} returns a reference from C++17 onwards

Author: PeterFeicht

headers/deque

@@ -186,7 +186,10 @@ public:
     void push_back(T&& value);
 #endif
 
-#if CPPREFERENCE_STDVER>= 2011
+#if CPPREFERENCE_STDVER >= 2017
+    template<class... Args>
+    reference emplace_back(Args&& ... args);
+#elif CPPREFERENCE_STDVER >= 2011
     template<class... Args>
     void emplace_back(Args&& ... args);
 #endif
@@ -198,7 +201,10 @@ public:
     void push_front(T&& value);
 #endif
 
-#if CPPREFERENCE_STDVER>= 2011
+#if CPPREFERENCE_STDVER >= 2017
+    template<class... Args>
+    reference emplace_front(Args&& ... args);
+#elif CPPREFERENCE_STDVER >= 2011
     template<class... Args>
     void emplace_front(Args&& ... args);
 #endif

headers/forward_list

@@ -129,8 +129,13 @@ public:
     void push_front(const T& value);
     void push_front(T&& value);
 
+#if CPPREFERENCE_STDVER >= 2017
+    template<class... Args>
+    reference emplace_front(Args&& ... args);
+#else
     template<class... Args>
     void emplace_front(Args&& ... args);
+#endif
 
     void pop_front();
 

headers/list

@@ -175,7 +175,10 @@ public:
     void push_back(T&& value);
 #endif
 
-#if CPPREFERENCE_STDVER>= 2011
+#if CPPREFERENCE_STDVER >= 2017
+    template<class... Args>
+    reference emplace_back(Args&& ... args);
+#elif CPPREFERENCE_STDVER >= 2011
     template<class... Args>
     void emplace_back(Args&& ... args);
 #endif
@@ -187,7 +190,10 @@ public:
     void push_front(T&& value);
 #endif
 
-#if CPPREFERENCE_STDVER>= 2011
+#if CPPREFERENCE_STDVER >= 2017
+    template<class... Args>
+    reference emplace_front(Args&& ... args);
+#elif CPPREFERENCE_STDVER >= 2011
     template<class... Args>
     void emplace_front(Args&& ... args);
 #endif

headers/vector

@@ -191,7 +191,10 @@ public:
     void push_back(T&& value);
 #endif
 
-#if CPPREFERENCE_STDVER>= 2011
+#if CPPREFERENCE_STDVER >= 2017
+    template<class... Args>
+    reference emplace_back(Args&& ... args);
+#elif CPPREFERENCE_STDVER >= 2011
     template<class... Args>
     void emplace_back(Args&& ... args);
 #endif