* comperr.adb (Compiler_Abort): Add a pair of pragma Warnings
On/Off to defend against a spurious warning in conditional
compilation.
* exp_ch4.adb (Rewrite_Comparison): Reimplemented.
* namet.adb (Finalize): Add a pair of pragma Warnings On/Off to
defend against a spurious warning in conditional compilation.
* output.adb Add a pair of pragma Warnings On/Off to defend
against a spurious warning in conditional compilation.
* sem_eval.adb (Eval_Relational_Op): Major code clean up.
(Fold_General_Op): New routine.
(Fold_Static_Real_Op): New routine.
(Test_Comparison): New routine.
* sem_eval.ads (Test_Comparison): New routine.
* sem_warn.adb (Is_Attribute_Constant_Comparison): New routine.
(Warn_On_Constant_Valid_Condition): New routine.
(Warn_On_Known_Condition): Use Is_Attribute_Constant_Comparison
to detect a specific case.
* sem_warn.adb (Warn_On_Constant_Valid_Condition): New routine.
* urealp.adb (Tree_Read): Add a pair of pragma Warnings On/Off
to defend against a spurious warning in conditional compilation.
(Tree_Write): Add a pair of pragma Warnings On/Off to defend
against a spurious warning in conditional compilation.
* usage.adb Add a pair of pragma Warnings On/Off to defend
against a spurious warning in conditional compilation.