tree.c (mapcar): When dealing with a DECL, use it's constant value, if any.

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	* tree.c (mapcar): When dealing with a DECL, use it's constant
	value, if any.
	* pt.c (lookup_template_class): Don't mangle the names of template
	classes whose arguments are unknown.
	* pt.c (tsubst_expr): Handle GOTO_STMT correctly.

From-SVN: r18805

gcc/testsuite/g++.old-deja/g++.pt/explicit68.C

@@ -0,0 +1,22 @@
+template <bool B>
+struct S
+{
+  static void g();
+};
+
+template <bool B>
+void g();
+
+template<unsigned Length>
+void f()
+{
+  const bool b = true;
+  g<b>();
+  const bool b1 = (Length == 2);
+  S<b1>::g();
+}
+
+void h()
+{
+  f<3>();
+}