patch 9.0.0253: a symlink to an autoload script results in two entries

Problem:    A symlink to an autoload script results in two entries in the list
            of scripts, items expected in one are actually in the other.
Solution:   Have one script item refer to the actually sourced one.
            (closes #10960)

src/evalvars.c

@@ -2953,6 +2953,7 @@ eval_variable(
 	    {
 		if (rettv != NULL)
 		{
+		    // special value that is used in handle_subscript()
 		    rettv->v_type = VAR_ANY;
 		    rettv->vval.v_number = sid != 0 ? sid : import->imp_sid;
 		}