[Ada] Use of Suppress_Initialization with pragma Thread_Local_Storage

[Ada] Use of Suppress_Initialization with pragma Thread_Local_Storage

This patch allows for aspect/pragma Suppress_Initialization to be an
acceptable form of missing initialization with respect to the semantics
of pragma Thread_Local_Storage.

------------
-- Source --
------------

--  gnat.adc

pragma Initialize_Scalars;

--  pack.ads

with System;

package Pack is
   Addr : System.Address
      with Thread_Local_Storage, Suppress_Initialization;
end Pack;

-----------------
-- Compilation --
-----------------

$ gcc -c pack.ads

2018-11-14  Hristian Kirtchev  <kirtchev@adacore.com>

gcc/ada/

	* freeze.adb (Check_Pragma_Thread_Local_Storage): New routine. A
	variable with suppressed initialization has no initialization
	for purposes of the pragma.
	(Freeze_Object_Declaration): Remove variable
	Has_Default_Initialization as it is no longer used. Use routine
	Check_Pragma_Thread_Local_Storage to verify the semantics of
	pragma Thread_Local_Storage.

From-SVN: r266129