* checks.adb (Insert_Valid_Check): Partially reimplement validity
checks.
* einfo.adb Node36 is now used as Validated_Object.
(Validated_Object): New routine.
(Set_Validated_Object): New routine.
(Write_Field36_Name): Add an entry for Validated_Object.
* einfo.ads Add new attribute Validated_Object along with
usage in entities.
(Validated_Object): New routine along with pragma Inline.
(Set_Validated_Object): New routine along with pragma Inline.
* exp_attr.adb (Make_Range_Test): Add processing for validation
variables to avoid extra reads and copies of the prefix.
* exp_ch6.adb (Expand_Actuals): Add copy-back for validation
variables in order to reflect any changes done in the variable
back into the original object.
* sem_util.adb (Is_Validation_Variable_Reference): New routine.
* sem_util.ads (Is_Validation_Variable_Reference): New routine.
* sem_prag.adb (Inherits_Class_Wide_Pre): subsidiary of
Analyze_Pre_Post_Condition, to implement the legality checks
mandated by AI12-0131: Pre'Class shall not be specified for an
overriding primitive subprogram of a tagged type T unless the
Pre'Class aspect is specified for the corresponding primitive
subprogram of some ancestor of T.