Modernisation: has_next() returns bool instead of long

src/iterator/grib_iterator.h

@@ -29,7 +29,7 @@ public:
     virtual int previous(double*, double*, double*) = 0;
     virtual int reset() = 0;
     virtual int destroy() = 0;
-    virtual long has_next() = 0;
+    virtual bool has_next() = 0;
     virtual Iterator* create() const = 0;
 
 public:

src/iterator/grib_iterator_class_gen.cc

@@ -88,13 +88,13 @@ int Gen::destroy()
     return Iterator::destroy();
 }
 
-long Gen::has_next()
+bool Gen::has_next()
 {
     if (flags_ == 0 && data_ == NULL)
-        return 0;
+        return false;
     if (e_ >= (long)(nv_ - 1))
-        return 0;
-    return 1;
+        return false;
+    return true;
 }
 
 int Gen::previous(double*, double*, double*) {

src/iterator/grib_iterator_class_gen.h

@@ -27,7 +27,7 @@ public:
     int previous(double*, double*, double*) override;
     int reset() override;
     int destroy() override;
-    long has_next() override; // TODO(maee/masn): return bool please!
+    bool has_next() override;
 
 public:
     //int get(double*, double*, double*);