[Ada] Fix misplaced error message

[Arnaud Charlet <charlet at adacore dot com>]

Tested on x86-linux, committed on mainline.

Fix misplaced error message.

Test case:
$ gcc -c test_it.adb
--
Error message was misplaced, expected output:
test_it.adb:10:23: prefix of Base attribute must be scalar type
--
procedure Test_It is
    type Int is range 1 .. 100;
    subtype S_Int is Int'Base range Int'Range;

    type N_Int is new Int'Base range Int'Range;

    type Rec is tagged null record;

    subtype S_Rec is Rec'Class;
    subtype S_Rec1 is Rec'Base;
begin
    null;
end Test_It;

2004-12-07  Ed Schonberg  <schonberg@adacore.com>

	* sem_ch8.adb (Find_Type): If node is a reference to 'Base and the
	prefix is not a scalar type, place error message on prefix, not on
	type entity.

Attachment: difs.22
Description: Text document