c++: Layout decls with newly-complete type.

c++: Layout decls with newly-complete type.

Martin's -Wplacement-new patch ran into a problem with DECL_SIZE not being
set on an extern variable for which the type was not complete until after
its declaration.  complete_vars was deliberately not calling layout_decl for
some reason, instead leaving that for expand_expr_real_1 much later in the
compilation.  But if we layout decls at declaration time, I don't see any
reason we shouldn't lay them out here, when their type is newly complete.

gcc/cp/ChangeLog:

	* decl.c (complete_vars): Call layout_var_decl.