C++: Moved all C++ examples to own folder

* moved C++ examples to a new cxx folder in
  examples
* added experimental C++ component
* added ESPException class to the C++ experimental
  component
* added test cases for ESPException and
  corresponding test macros

examples/cxx/rtti/main/rtti_example_main.cpp

@@ -0,0 +1,100 @@
+/* C++ run-time type info (RTTI) example
+
+   This example code is in the Public Domain (or CC0 licensed, at your option.)
+
+   Unless required by applicable law or agreed to in writing, this
+   software is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
+   CONDITIONS OF ANY KIND, either express or implied.
+*/
+
+#include <iostream>
+#include <memory>
+#include <vector>
+#include <algorithm>
+#include <cxxabi.h>
+
+using std::cout;
+using std::endl;
+using std::string;
+using std::shared_ptr;
+using std::make_shared;
+
+class Base;
+class DerivedA;
+class DerivedB;
+
+static string demangle(const char* name);
+
+class Base
+{
+public:
+    virtual ~Base() {} ;
+    virtual string name() = 0;
+    static shared_ptr<Base> make_random_derived();
+};
+
+class DerivedA : public Base
+{
+public:
+    string name() override { return "DerivedA"; }
+};
+
+class DerivedB : public Base
+{
+public:
+    string name() override { return "DerivedB"; }
+};
+
+/* Creates either DerivedA or DerivedB, depending on a random number */
+shared_ptr<Base> Base::make_random_derived()
+{
+    if (std::rand() % 2 == 0) {
+        return make_shared<DerivedA>();
+    } else {
+        return make_shared<DerivedB>();
+    }
+}
+
+/* Inside a .cpp file, app_main function must be declared with C linkage */
+extern "C" void app_main()
+{
+    /* Demonstrate typeid().name() */
+    cout << "Type names of a few objects:" << endl << '\t';
+    cout << "Type name of std::cout is: " << demangle(typeid(std::cout).name()) << endl << '\t';
+    cout << "Type name of std::cin is: "  << demangle(typeid(std::cin).name()) << endl << '\t';
+    cout << "Type of app_main is: " << demangle(typeid(app_main).name()) << endl << '\t';
+    auto sum = [](int x, int y) -> int { return x + y; };
+    cout << "Type name of a lambda function is: "  << demangle(typeid(sum).name()) << endl << endl;
+
+    /* Demonstrate dynamic_cast */
+    std::vector<shared_ptr<Base>> objects(5);
+    cout << "Generating " << objects.size() << " random objects and printing their types:" << endl;
+    std::generate(objects.begin(), objects.end(), Base::make_random_derived);
+    for (auto &obj: objects) {
+        cout << "obj->name() is: " << obj->name() << endl << '\t';
+        cout << "typeid(*obj).name() is: " << demangle(typeid(*obj).name()) << endl << '\t';
+        
+        const DerivedA* cast_to_derived_a = dynamic_cast<DerivedA*>(obj.get());
+        const DerivedB* cast_to_derived_b = dynamic_cast<DerivedB*>(obj.get());
+
+        cout << "dynamic_cast<DerivedA*>(obj)=" << static_cast<const void*>(cast_to_derived_a) << endl << '\t';
+        cout << "dynamic_cast<DerivedB*>(obj)=" << static_cast<const void*>(cast_to_derived_b) << endl << endl;
+    }
+
+    cout << "Example finished." << endl;
+}
+
+/* Helper function which converts typeid().name() to a human-readable type name */
+static std::string demangle(const char* name)
+{
+    int status = 0;
+    char* result = abi::__cxa_demangle(name, NULL, NULL, &status);
+    string str_result;
+    if (status == 0) {
+        str_result = result;
+    } else {
+        str_result = name;
+    }
+    free(result);
+    return str_result;
+}