decl.c (gnat_to_gnu_entity): Generate an XVZ variable alongside the XVS type if the size is not constant.

	* gcc-interface/decl.c (gnat_to_gnu_entity) <E_Record_Subtype>:
	Generate an XVZ variable alongside the XVS type if the size is
	not constant.
	(maybe_pad_type): Minor tweak.

From-SVN: r152420