[Ada] Fix incompatibility Default_Scalar_Storage_Order/tagged types

[Ada] Fix incompatibility Default_Scalar_Storage_Order/tagged types

The pragma Default_Scalar_Storage_Order cannot reliably be used to set the
non-default scalar storage order for a program that declares tagged types, if
it also declares user-defined primitives.

This is fixed by making Make_Tags use the same base array type as Make_DT and
Make_Secondary_DT when accessing the array of user-defined primitives.

2018-07-17  Eric Botcazou  <ebotcazou@adacore.com>

gcc/ada/

	* exp_disp.adb (Make_Tags): When the type has user-defined primitives,
	build the access type that is later used by Build_Get_Prim_Op_Address
	as pointing to a subtype of Ada.Tags.Address_Array.

gcc/testsuite/

	* gnat.dg/sso10.adb, gnat.dg/sso10_pkg.ads: New testcase.

From-SVN: r262797