Fix cppcheck struct member is never used. [unusedStructMember]

src/Collgrid.cc

@@ -33,7 +33,6 @@ struct EnsfileType
 {
   CdoStreamID streamID;
   int vlistID;
-  int gridID;
   size_t nmiss;
   size_t gridsize;
   std::vector<long> gridindex;

src/Detrend.cc

@@ -35,7 +35,7 @@
 #define NALLOC_INC 1024
 
 static void
-detrend(const long nts, Varray<double> &deltaTS0, const double missval1, const Varray<double> &array1, Varray<double> &array2)
+detrend(const long nts, const Varray<double> &deltaTS0, const double missval1, const Varray<double> &array1, Varray<double> &array2)
 {
   const auto missval2 = missval1;
   double sumj = 0, sumjj = 0;

src/Samplegrid.cc

@@ -77,8 +77,6 @@ Samplegrid(void *process)
   struct sbox_t
   {
     int gridSrcID, gridIDsampled;
-    int *cellidx, nvals;
-    int subI0, subI1, subJ0, subJ1;
   };
 
   cdoInitialize(process);