Add C++ lamba example.

tests/hellolambda/.gitignore

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+hellolambda
+*.seer
+core.*

tests/hellolambda/Makefile

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+.PHONY: all
+all: hellolambda
+
+hellolambda: hellolambda.cpp
+	g++ -g -o hellolambda hellolambda.cpp
+
+.PHONY: clean
+clean:
+	rm -f hellolambda hellolambda.o
+

tests/hellolambda/README

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+
+
+See this article about debugging lambdas.
+
+gdb/mi is missing 'skip' and 'checkpoint' and 'restart' commands.
+
+https://developers.redhat.com/articles/2023/05/03/how-debug-c-lambda-expressions-gdb#
+
+

tests/hellolambda/hellolambda.cpp

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+#include <stdio.h>
+#include <functional>
+
+int successor (int i) { return i + 1; }
+
+int apply0 (int (*fn)(int), int arg)
+{
+  return fn (arg);
+}
+
+int apply1 (std::function<int(int)> fn, int arg)
+{
+  return fn (arg);
+}
+
+std::function<int(int)> make_function(int& x) {
+    return [&] (int i) { return i + x; };               /* Line 17 */
+}
+
+int main (int argc, char **argv)
+{
+  int n = 7, m = -28;
+
+  printf ("Answer 1 is %d\n", apply0 (successor, 3));   /* Line 24 */
+  printf ("Answer 2 is %d\n", apply1 (successor, 4));   /* Line 25 */
+
+  printf ("Answer 3 is %d\n",
+          apply0 ([] (int i) { return i + 1; }, 1));    /* Line 28 */
+  printf ("Answer 4 is %d\n",
+          apply1 ([] (int i) { return i + 1; }, 2));    /* Line 30 */
+
+  printf ("Answer 5 is %d\n",
+          apply1 ([n] (int i) { return i + n; }, 4));   /* Line 33 */
+
+  auto lf2 = make_function (n);                         /* Line 35 */
+  printf ("Answer 6 is %d\n", apply1 (lf2, 1));         /* Line 36 */
+
+  auto lf3 = make_function (m);
+  printf ("Answer 7 is %d\n", apply1 (lf3, -14));       /* Line 39 */
+
+  return 0;
+}
+
+//
+// Keep line numbers to match this article about debugging lambdas.
+// https://developers.redhat.com/articles/2023/05/03/how-debug-c-lambda-expressions-gdb#
+//
+