File fix-gcc7.patch of Package kadu

Index: kadu-core/plugin/dependency-graph/plugin-dependency-graph-builder.h
===================================================================
--- kadu-core/plugin/dependency-graph/plugin-dependency-graph-builder.h.orig
+++ kadu-core/plugin/dependency-graph/plugin-dependency-graph-builder.h
@@ -22,6 +22,7 @@
 #include <QtCore/QObject>
 #include <map>
 #include <set>
+#include <functional>
 
 #include "plugin/dependency-graph/plugin-dependency-graph.h"
 #include "exports.h"
Index: CMakeLists.txt
===================================================================
--- CMakeLists.txt.orig
+++ CMakeLists.txt
@@ -39,6 +39,7 @@ else ()
 	set (C_FLAGS "-Wwrite-strings")
 	set (CXX_FLAGS "-Woverloaded-virtual -Wnon-virtual-dtor ${CXX_FLAGS}")
 	set (CMAKE_CXX_STANDARD 14)
+    set (CXX_STANDARD_REQUIRED ON)
 
 	if (NOT WIN32)
 		set (COMMON_COMPILE_FLAGS "${COMMON_COMPILE_FLAGS} -fvisibility=hidden")