[Ada] Fix propagation of compiler internal flag

[Ada] Fix propagation of compiler internal flag

No change in behavior for GCC-based compilations.

2019-08-20  Ed Schonberg  <schonberg@adacore.com>

gcc/ada/

	* sem_ch3.adb (Analyze_Object_Declaration): If actual type is
	private and distinct from nominal type in declaration, propagate
	flags Is_Constr_Subt_For_U_Nominal and _UN_Aliased to full view
	of private type.

From-SVN: r274735