[Ada] Spurious Storage_Error on imported array

[Ada] Spurious Storage_Error on imported array

This patch moves the check which verifies that a large modular array is created
from expansion to freezing in order to take interfacing pragmas in account. The
check is no longer performed on imported objects because no object is created
in that case.

2018-05-23  Hristian Kirtchev  <kirtchev@adacore.com>

gcc/ada/

	* exp_ch3.adb (Check_Large_Modular_Array): Moved to Freeze.
	(Expand_N_Object_Declaration): Do not check for a large modular array
	here.
	* freeze.adb (Check_Large_Modular_Array): Moved from Exp_Ch3.
	(Freeze_Object_Declaration): Code cleanup. Check for a large modular
	array.
	* sem_ch3.adb: Minor reformatting.

gcc/testsuite/

	* gnat.dg/import2.adb: New testcase.

From-SVN: r260597