Fix compatibility with C++17.

Signed-off-by: Slávek Banko <slavek.banko@axis.cz>

src/base/AnalysisTypes.h

@@ -27,6 +27,7 @@
 #include <map>
 #include <set>
 #include <vector>
+#include <functional>
 
 #include "NotationTypes.h"
 
@@ -157,7 +158,7 @@ protected:
     typedef std::pair<double, ChordLabel> ChordPossibility;
     typedef std::vector<ChordPossibility> HarmonyGuess;
     typedef std::vector<std::pair<timeT, HarmonyGuess> > HarmonyGuessList;
-    struct cp_less : public std::binary_function<ChordPossibility, ChordPossibility, bool>
+    struct cp_less : public std::function<bool(ChordPossibility, ChordPossibility)>
     {
         bool operator()(ChordPossibility l, ChordPossibility r);
     };