Fix more Fortran warnings

Author: cschwan

examples/fortran/pineappl.f90

@@ -607,15 +607,15 @@ integer function pineappl_grid_bin_count(grid)
 
         type (pineappl_grid), intent(in) :: grid
 
-        pineappl_grid_bin_count = grid_bin_count(grid%ptr)
+        pineappl_grid_bin_count = int(grid_bin_count(grid%ptr))
     end function
 
     integer function pineappl_grid_bin_dimensions(grid)
         implicit none
 
         type (pineappl_grid), intent(in) :: grid
 
-        pineappl_grid_bin_dimensions = grid_bin_dimensions(grid%ptr)
+        pineappl_grid_bin_dimensions = int(grid_bin_dimensions(grid%ptr))
     end function
 
     function pineappl_grid_bin_limits_left(grid, dimension) result(res)
@@ -949,8 +949,6 @@ type (pineappl_grid) function pineappl_grid_new2(bins, bin_limits, orders, order
         type (pineappl_interp), dimension(interpolations), intent(in)             :: interp_info
         type (pineappl_scale_func_form), dimension(interpolations)                :: mu_scales
 
-        integer :: i
-
         pineappl_grid_new2 = pineappl_grid(grid_new2(&
             int(bins, c_size_t), &
             bin_limits, &