Fix bug in fld_type_variant

[Jan Hubicka]

Hi,
in fld_type_variant I lost code copying alignment. This patch fixes it
and also checks that newly constructed variant is indeed compatible.

Bootstrapped/regtested x86_64-linux, comitted as obvious.

Honza
        * tree.c (fld_type_variant): Also copy alignment; be sure that
        new variant is equal.
Index: tree.c
===================================================================
--- tree.c      (revision 265841)
+++ tree.c      (working copy)
@@ -5119,6 +5119,8 @@ fld_type_variant (tree first, tree t, st
   TYPE_NAME (v) = TYPE_NAME (t);
   TYPE_ATTRIBUTES (v) = TYPE_ATTRIBUTES (t);
   TYPE_CANONICAL (v) = TYPE_CANONICAL (t);
+  SET_TYPE_ALIGN (v, TYPE_ALIGN (t));
+  gcc_checking_assert (fld_type_variant_equal_p (t,v));
   add_tree_to_fld_list (v, fld);
   return v;
 }