[Ada] Get rid of more references to Universal_Integer in expanded code

[Pierre-Marie de Rodat]

This fixes a couple of places to using the standard idiom for choosing
an appropriately-sized integer type.  No practical change since the old
and the new type are effectively identical.

Tested on x86_64-pc-linux-gnu, committed on trunk

2020-06-03  Eric Botcazou  <ebotca...@adacore.com>

gcc/ada/

        * exp_attr.adb (Attribute_Valid): Use Standard_Long_Long_Integer
        in lieu of Universal_Integer as large integer type.
        * exp_ch3.adb (Expand_Freeze_Enumeration_Type): Likewise.
--- gcc/ada/exp_attr.adb
+++ gcc/ada/exp_attr.adb
@@ -6924,7 +6924,7 @@ package body Exp_Attr is
             if Esize (Ptyp) <= Esize (Standard_Integer) then
                PBtyp := Standard_Integer;
             else
-               PBtyp := Universal_Integer;
+               PBtyp := Standard_Long_Long_Integer;
             end if;
 
             Rewrite (N, Make_Range_Test);

--- gcc/ada/exp_ch3.adb
+++ gcc/ada/exp_ch3.adb
@@ -4806,7 +4806,7 @@ package body Exp_Ch3 is
          if Esize (Typ) <= Standard_Integer_Size then
             Ityp := Standard_Integer;
          else
-            Ityp := Universal_Integer;
+            Ityp := Standard_Long_Long_Integer;
          end if;
 
       --  Representations are unsigned