Rewriters to move to Ada202x code

[pjljvandelaar]

See https://blog.adacore.com/ada-202x-support-in-gnat

e.g. replace

for E of Some_Array loop
   if E /= 0 then
      Put_Line (E'Image);
   end if;
end loop;

by

for E of Some_Array when E /= 0 loop
   Put_Line (E'Image);
end loop;

[pjljvandelaar]

Vector initialization

Replace

for I in 1..N loop Append (V, I*2); end loop;

by

V = [for I in 1..N => I * 2];

[pjljvandelaar]

Use reduce

Replace

declare
   sum : Integer := $S_Initial;
begin
   for E of $S_Container loop
        sum := sum + $S_Add;
   end loop;
   $M_Stmts;
end;

by

declare
   sum : Integer := [for E of $S_Container => $S_Add].Reduce ("+", $S_Initial);
begin
   $M_Stmts;
end;

And we even might check whether we can add the constant keyword to the declaration of sum