Fix C++17 compilation warning

src/Connection.cpp

@@ -149,7 +149,7 @@ ConnectionInfo Connection::info(int index)
 }
 
 
-struct hasName: public std::unary_function<ConnectionInfo, bool>
+struct hasName
 {
     inline bool operator()(const ConnectionInfo &elem) const {
        return (elem.name.compare(_a) == 0);

src/FrameGrabber.cpp

@@ -84,7 +84,7 @@ bool FrameGrabbing::busy() const
     return !grabbers_.empty();
 }
 
-struct fgId: public std::unary_function<FrameGrabber*, bool>
+struct fgId
 {
     inline bool operator()(const FrameGrabber* elem) const {
        return (elem && elem->id() == _id);

src/Scene.h

@@ -132,9 +132,9 @@ typedef std::multiset<Node*, z_comparator> NodeSet;
 
 //typedef std::list<Node*> NodeSet;
 
-struct hasId: public std::unary_function<Node*, bool>
+struct hasId
 {
-    inline bool operator()(const Node* e) const
+    constexpr bool operator()(const Node* e) const
     {
        return (e && e->id() == _id);
     }

src/Source.h

@@ -200,7 +200,7 @@ public:
     MixingGroup *mixingGroup() const { return mixinggroup_; }
     void clearMixingGroup();
 
-    struct hasNode: public std::unary_function<Source*, bool>
+    struct hasNode
     {
         bool operator()(const Source* elem) const;
         hasNode(Node *n) : _n(n) { }
@@ -208,7 +208,7 @@ public:
         Node *_n;
     };
 
-    struct hasName: public std::unary_function<Source*, bool>
+    struct hasName
     {
         inline bool operator()(const Source* elem) const {
            return (elem && elem->name() == _n);
@@ -218,7 +218,7 @@ public:
         std::string _n;
     };
 
-    struct hasId: public std::unary_function<Source*, bool>
+    struct hasId
     {
         inline bool operator()(const Source* elem) const {
            return (elem && elem->id() == _id);
@@ -228,7 +228,7 @@ public:
         uint64_t _id;
     };
 
-    struct hasDepth: public std::unary_function<Source*, bool>
+    struct hasDepth
     {
         inline bool operator()(const Source* elem) const {
            return (elem && elem->depth()>_from && elem->depth()<_to );

src/Timeline.cpp

@@ -28,7 +28,7 @@
 static float empty_zeros[MAX_TIMELINE_ARRAY] = {};
 static float empty_ones[MAX_TIMELINE_ARRAY] = {};
 
-struct includesTime: public std::unary_function<TimeInterval, bool>
+struct includesTime
 {
     inline bool operator()(const TimeInterval s) const
     {