sem_ch3.adb (Check_Or_Process_Discriminants): In Ada 2012, allow limited tagged types...

sem_ch3.adb (Check_Or_Process_Discriminants): In Ada 2012, allow limited tagged types to have defaulted discriminants.

2010-10-22  Gary Dismukes  <dismukes@adacore.com>

	* sem_ch3.adb (Check_Or_Process_Discriminants): In Ada 2012, allow
	limited tagged types to have defaulted discriminants. Customize the
	error message for the Ada 2012 case.
	(Process_Discriminants): In Ada 2012, allow limited tagged types to have
	defaulted discriminants. Customize the error message for the Ada 2012
	case.
	* sem_ch6.adb (Create_Extra_Formals): Suppress creation of the extra
	formal for out formals of discriminated types in the case where the
	underlying type is a limited tagged type.
	* exp_attr.adb (Expand_N_Attribute_Reference, case
	Attribute_Constrained): Return True for 'Constrained when the
	underlying type of the prefix is a limited tagged type.

From-SVN: r165819