Intel compiler 2021.3.0 fixes

These changes were needed in order to compile with the latest intel 2021.3.0 compiler on Piz Daint.

alpine/LandauDamping.cpp

@@ -199,7 +199,7 @@ int main(int argc, char *argv[]){
 
     // create mesh and layout objects for this problem domain
     Vector_t kw = {0.5, 0.5, 0.5};
-    double alpha = 0.5;
+    double alpha = 0.05;
     Vector_t rmin(0.0);
     Vector_t rmax = 2 * pi / kw ;
     double dx = rmax[0] / nr[0];