Let -Ra/e for grdtrack for remote data sets.

`gmt grdtrack @ship_15.txt -q1-100 -G@earth_relief_06m -Ra`

In the command above it is useful to define the region of the profile because otherwise the whole remote datasets are download.

I try it but it didn't work,

```
grdtrack [WARNING]: No country code matching a (skipped)
grdtrack (GMT_grdtrack): Subset y range <= 0.0
```