[clang] [clang] Accept lambdas in C++03 as an extensions (PR #73376)

[Aaron Ballman via cfe-commits]

================
@@ -0,0 +1,5 @@
+// RUN: %clang_cc1 -fsyntax-only -Wno-unused-value -verify -std=c++03 %s
+
+void func() {
----------------
AaronBallman wrote:

We should also test that `__has_feature(cxx_lambdas)` produces the correct results -- I think you're missing changes in `include/clang/Basic/Features.def`.

https://github.com/llvm/llvm-project/pull/73376