* errout.adb (Error_Msg_NEL): Use Suppress_Loop_Warnings rather than
Is_Null_Loop to suppress warnings in a loop body.
* exp_ch4.adb:
(Rewrite_Comparison): Major rewrite to accomodate invalid values
* exp_ch5.adb:
(Expand_N_Loop_Statement): Delete loop known not to execute
* opt.ads:
(Assume_No_Invalid_Values): Now set to False, and as documented, this
fully enables the proper handling of invalid values.
* sem_attr.adb:
New calling sequence for Is_In_Range
* sem_ch5.adb:
(Analyze_Iteration_Scheme): Accomodate possible invalid values
in determining if a loop range is null.
* sem_eval.adb:
(Is_In_Range): Add Assume_Valid parameter
(Is_Out_Of_Range): Add Assume_Valid_Parameter
(Compile_Time_Compare): Major rewrite to accomodate invalid values and
also to do more accurate and complete range analysis, catching more
cases.