[Ada] Ignore switches for controlling frontend warnings in GNATprove mode
In the special mode for GNATprove, ignore switches controlling frontend
warnings, like already done for the control of style checks warnings.
Also remove special handling of warning mode in Errout to make up for
the previous division of control between -gnatw (GNAT) and --warnings
(GNATprove).
gcc/ada/
* errout.adb (Record_Compilation_Errors): Remove global
variable.
(Compilation_Errors): Simplify.
(Initialize): Inline Reset_Warnings.
(Reset_Warnings): Remove.
* errout.ads (Reset_Warnings): Remove.
(Compilation_Errors): Update comment.
* gnat1drv.adb (Adjust_Global_Switches): Ignore all frontend
warnings in GNATprove mode, except regarding elaboration and
suspicious contracts.