replace variable length array in Molecule class with new/delete

src/molecule.cpp

@@ -1111,7 +1111,7 @@ void Molecule::special_generate()
 {
   int newton_bond = force->newton_bond;
   tagint atom1,atom2;
-  int count[natoms];
+  int *count = new int[natoms];
 
   // temporary array for special atoms
 
@@ -1197,6 +1197,7 @@ void Molecule::special_generate()
       }
     }
   }
+  delete[] count;
 
   maxspecial = 0;
   for (int i = 0; i < natoms; i++)