!topic attribute_designator misses Mod keyword
!reference Ada 2005 RM 4.1.4(3)
!from Maxim Reznik 07-12-26
!keywords mod attribute designator
!discussion
New attribute Mod was introduced in RM-3.5.4(16.1/2).
Mod is reserved keyword according to RM-2.9 (2.b), so
attribute_designator syntax rule should include it:

 attribute_designator ::=
   identifier[(static_expression)]
 | Access | Delta | Digits | Mod