Shift the longitude of the polyline

So that it is in the grid.

Inst_eddies/Tests/test_mean_speed.f90

@@ -28,6 +28,7 @@ program test_mean_speed
   TYPE(shpobject) psobject
   type(polygon) p
   character(len = :), allocatable:: contour_filename
+  real min_lon_p ! minimum longitude of p, in degrees
 
   namelist /main_nml/ center, ishape
 
@@ -71,6 +72,12 @@ program test_mean_speed
   CALL shpclose(hshp)
   p = shpobj2pol(psobject)
   call shpdestroyobject(psobject)
+
+  ! Shift the longitude of the polyline so that it is in the grid:
+  min_lon_p = minval(p%part(1)%points(1, :))
+  p%part(1)%points(1, :) = p%part(1)%points(1, :) &
+       + ceiling((corner(1) - min_lon_p) / 360.) * 360.
+  
   p%part(1)%points = p%part(1)%points * deg_to_rad
   print *, "mean azimuthal speed = ", mean_speed(u, v, p%part(1), &
        center * deg_to_rad, corner * deg_to_rad, step  * deg_to_rad), "m s-1"