c++: Add testcase for issue fixed in GCC 15 [PR120126]

Patrick noticed that this PR's testcase has been fixed by the patch for
PR c++/114292 (r15-7238-gceabea405ffdc8), more specifically the part
that walks the type of DECL_EXPR DECLs.

This simply adds the case to the testsuite.

	PR c++/120126

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/lambda/lambda-ice33.C: New test.

Author: simartin

gcc/testsuite/g++.dg/cpp0x/lambda/lambda-ice33.C

@@ -0,0 +1,12 @@
+// PR c++/120126
+// { dg-do compile { target c++11 } }
+
+template <typename... Args>
+int sum(Args... args) {
+  return [args...] { // { dg-error "parameter packs not expanded with" }
+    typename decltype(args)::type temp;
+  };
+}
+int main() {
+  sum(1, 10);
+}