Image scale dialog: use two decimal places

GIMP does as well, and it provides better information.

It's not as if anyone is really going to use the spin button features
which behave weird with this, and it indicates that decimal numbers may
be written at all.

fiv-view.c

@@ -1506,7 +1506,7 @@ zoom_ask(FivView *self)
 	// For example, we would like to be flexible with decimal spaces.
 	GtkAdjustment *adjustment = gtk_adjustment_new(
 		self->scale * 100, 0., 100000., 1., 10., 0.);
-	GtkWidget *spin = gtk_spin_button_new(adjustment, 1., 0);
+	GtkWidget *spin = gtk_spin_button_new(adjustment, 1., 2);
 	gtk_spin_button_set_update_policy(
 		GTK_SPIN_BUTTON(spin), GTK_UPDATE_IF_VALID);
 	gtk_entry_set_activates_default(GTK_ENTRY(spin), TRUE);