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/pthread/main/cpp_pthread.cpp

@@ -0,0 +1,112 @@
+/* pthread/std::thread 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 <thread>
+#include <chrono>
+#include <memory>
+#include <string>
+#include <sstream>
+#include <esp_pthread.h>
+#include <freertos/FreeRTOS.h>
+#include <freertos/task.h>
+#include <esp_log.h>
+
+using namespace std::chrono;
+
+const auto sleep_time = seconds
+{
+    5
+};
+
+void print_thread_info(const char *extra = nullptr)
+{
+    std::stringstream ss;
+    if (extra) {
+        ss << extra;
+    }
+    ss << "Core id: " << xPortGetCoreID()
+       << ", prio: " << uxTaskPriorityGet(nullptr)
+       << ", minimum free stack: " << uxTaskGetStackHighWaterMark(nullptr) << " bytes.";
+    ESP_LOGI(pcTaskGetTaskName(nullptr), "%s", ss.str().c_str());
+}
+
+void thread_func_inherited()
+{
+    while (true) {
+        print_thread_info("This is the INHERITING thread with the same parameters as our parent, including name. ");
+        std::this_thread::sleep_for(sleep_time);
+    }
+}
+
+void spawn_another_thread()
+{
+    // Create a new thread, it will inherit our configuration
+    std::thread inherits(thread_func_inherited);
+
+    while (true) {
+        print_thread_info();
+        std::this_thread::sleep_for(sleep_time);
+    }
+}
+
+void thread_func_any_core()
+{
+    while (true) {
+        print_thread_info("This thread (with the default name) may run on any core.");
+        std::this_thread::sleep_for(sleep_time);
+    }
+}
+
+void thread_func()
+{
+    while (true) {
+        print_thread_info();
+        std::this_thread::sleep_for(sleep_time);
+    }
+}
+
+esp_pthread_cfg_t create_config(const char *name, int core_id, int stack, int prio)
+{
+    auto cfg = esp_pthread_get_default_config();
+    cfg.thread_name = name;
+    cfg.pin_to_core = core_id;
+    cfg.stack_size = stack;
+    cfg.prio = prio;
+    return cfg;
+}
+
+extern "C" void app_main(void)
+{
+    // Create a thread using deafult values that can run on any core
+    auto cfg = esp_pthread_get_default_config();
+    esp_pthread_set_cfg(&cfg);
+    std::thread any_core(thread_func_any_core);
+
+    // Create a thread on core 0 that spawns another thread, they will both have the same name etc.
+    cfg = create_config("Thread 1", 0, 3 * 1024, 5);
+    cfg.inherit_cfg = true;
+    esp_pthread_set_cfg(&cfg);
+    std::thread thread_1(spawn_another_thread);
+
+    // Create a thread on core 1.
+    cfg = create_config("Thread 2", 1, 3 * 1024, 5);
+    esp_pthread_set_cfg(&cfg);
+    std::thread thread_2(thread_func);
+
+    // Let the main task do something too
+    while (true) {
+        std::stringstream ss;
+        ss << "core id: " << xPortGetCoreID()
+           << ", prio: " << uxTaskPriorityGet(nullptr)
+           << ", minimum free stack: " << uxTaskGetStackHighWaterMark(nullptr) << " bytes.";
+        ESP_LOGI(pcTaskGetTaskName(nullptr), "%s", ss.str().c_str());
+        std::this_thread::sleep_for(sleep_time);
+    }
+}