[Ada] More complete information level for -gnatR4 output

[Ada] More complete information level for -gnatR4 output

This instructs -gnatR4 to also list the Etype of a user-declared record
subtype if it is compiler-generated, for example in:

package P is

   type U_Arr is array (Integer range <>) of Character;

   type Rec1 (D1, D2 : Integer) is record
      C : U_Arr (D1 .. D2);
   end record;

   type Rec_N is new Rec1 (1, 2);

end P;

2019-08-20  Eric Botcazou  <ebotcazou@adacore.com>

gcc/ada/

	* repinfo.adb (List_Record_Info): In -gnatR4 mode, set the
	relevant flag on the implicit base type of a record subtype.

From-SVN: r274727