class inherits private attributes with identical names

[larshp]

similar to #1488 but for attributes

[larshp]

expected value = "2"

CLASS top DEFINITION.
  PUBLIC SECTION.
    METHODS call RETURNING VALUE(result) TYPE i.
  PRIVATE SECTION.
    DATA foo TYPE i VALUE 2.
ENDCLASS.
CLASS top IMPLEMENTATION.
  METHOD call.
    result = foo.
  ENDMETHOD.
ENDCLASS.

CLASS sub DEFINITION INHERITING FROM top.
  PUBLIC SECTION.
  PRIVATE SECTION.
    DATA foo TYPE i VALUE 1.
ENDCLASS.
CLASS sub IMPLEMENTATION.
ENDCLASS.

START-OF-SELECTION.
  DATA lo TYPE REF TO sub.
  CREATE OBJECT lo.
  WRITE lo->call( ).