examples: cleanup examples directory

Following changes are done as a part of cleanup:

1. Moved the platform specific `C` examples from top level examples/
directory to platform/ subdirectory and renamed helloedison.c to
gpio_edison.c

2. C specific examples are moved to a new c/ subdirectory. As a part
of this process, examples are modified to follow same standards
and few new examples are also added.

3. Include the newly added C examples to relevant API documentation

4. Ran clang-format for all source files in c/, c++/, platform/
subdirectories

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>

examples/c/gpio.c

@@ -0,0 +1,147 @@
+/*
+ * Author: Thomas Ingleby <thomas.c.ingleby@intel.com>
+ * Contributors: Alex Tereschenko <alext.mkrs@gmail.com>
+ * Contributors: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
+ * Copyright (c) 2014 Intel Corporation.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * Example usage: Toggles GPIO's 23 and 24 recursively. Press Ctrl+C to exit
+ *
+ */
+
+/* standard headers */
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+/* mraa header */
+#include "mraa/gpio.h"
+
+/* gpio declaration */
+#define GPIO_PIN_1 23
+#define GPIO_PIN_2 24
+
+volatile sig_atomic_t flag = 1;
+
+void
+sig_handler(int signum)
+{
+    if (signum == SIGINT) {
+        fprintf(stdout, "Exiting...\n");
+        flag = 0;
+    }
+}
+
+int
+main(void)
+{
+    mraa_result_t status = MRAA_SUCCESS;
+    mraa_gpio_context gpio_1, gpio_2;
+
+    /* install signal handler */
+    signal(SIGINT, sig_handler);
+
+    /* initialize mraa for the platform (not needed most of the times) */
+    mraa_init();
+
+    //! [Interesting]
+    /* initialize GPIO pin */
+    gpio_1 = mraa_gpio_init(GPIO_PIN_1);
+    if (gpio_1 == NULL) {
+        fprintf(stderr, "Failed to initialize GPIO %d\n", GPIO_PIN_1);
+        mraa_deinit();
+        return EXIT_FAILURE;
+    }
+
+    /* initialize GPIO pin */
+    gpio_2 = mraa_gpio_init(GPIO_PIN_2);
+    if (gpio_2 == NULL) {
+        fprintf(stderr, "Failed to initialize GPIO %d\n", GPIO_PIN_2);
+        mraa_deinit();
+        return EXIT_FAILURE;
+    }
+
+    /* set GPIO to output */
+    status = mraa_gpio_dir(gpio_1, MRAA_GPIO_OUT);
+    if (status != MRAA_SUCCESS) {
+        goto err_exit;
+    }
+
+    /* set GPIO to output */
+    status = mraa_gpio_dir(gpio_2, MRAA_GPIO_OUT);
+    if (status != MRAA_SUCCESS) {
+        goto err_exit;
+    }
+
+    /* toggle both GPIO's */
+    while (flag) {
+        status = mraa_gpio_write(gpio_1, 1);
+        if (status != MRAA_SUCCESS) {
+            goto err_exit;
+        }
+
+        status = mraa_gpio_write(gpio_2, 0);
+        if (status != MRAA_SUCCESS) {
+            goto err_exit;
+        }
+
+        sleep(1);
+
+        status = mraa_gpio_write(gpio_1, 0);
+        if (status != MRAA_SUCCESS) {
+            goto err_exit;
+        }
+
+        status = mraa_gpio_write(gpio_2, 1);
+        if (status != MRAA_SUCCESS) {
+            goto err_exit;
+        }
+
+        sleep(1);
+    }
+
+    /* release gpio's */
+    status = mraa_gpio_close(gpio_1);
+    if (status != MRAA_SUCCESS) {
+        goto err_exit;
+    }
+
+    /* close GPIO */
+    status = mraa_gpio_close(gpio_2);
+    if (status != MRAA_SUCCESS) {
+        goto err_exit;
+    }
+
+    //! [Interesting]
+    /* deinitialize mraa for the platform (not needed most of the times) */
+    mraa_deinit();
+
+    return EXIT_SUCCESS;
+
+err_exit:
+    mraa_result_print(status);
+
+    /* deinitialize mraa for the platform (not needed most of the times) */
+    mraa_deinit();
+
+    return EXIT_FAILURE;
+}