Niels De Graef authored Aug 20, 2019 and Jehan committed May 10, 2020

`gimp_unit_store_get_value()` clashes with the `get_value()` method of
its parent class GtkTreeStore. This means trouble for bindings, as seen
here in some pseudocode:

```vala
var unit_store = new Gimp.UnitStore();
// Which function are we referencing here, the one from GtkTreeStore or
// the one from GimpUnitStore? Worse, they both have different arguments
unit_store.get_value( ... )
```