In some cases where the size computation for an object declaration will
unconditionally overflow, the FE generates code to raise Storage_Error
at the point of the object declaration (and may generate an associated
warning). Don't do this if the object declaration is an ignored (i.e.,
disabled) ghost declaration.

Tested on x86_64-pc-linux-gnu, committed on trunk

2019-09-18  Steve Baird  <baird@adacore.com>

gcc/ada/

	* freeze.adb (Freeze_Object_Declaration): Do not call
	Check_Large_Modular_Array when the object declaration being
	frozen is an ignored ghost entity.

gcc/testsuite/

	* gnat.dg/ghost7.adb, gnat.dg/ghost7.ads: New testcase.