Update the API examples to use print from extensions (#1846)

JerryScript-DCO-1.0-Signed-off-by: László Langó llango.u-szeged@partner.samsung.com

docs/03.API-EXAMPLE.md

@@ -11,7 +11,7 @@ This guide is intended to introduce you to JerryScript embedding API through cre
 int
 main (int argc, char *argv[])
 {
-  const jerry_char_t script[] = "print ('Hello, World!');";
+  const jerry_char_t script[] = "var str = 'Hello, World!';";
   size_t script_size = strlen ((const char *) script);
 
   bool ret_value = jerry_run_simple (script, script_size, JERRY_INIT_EMPTY);
@@ -20,11 +20,7 @@ main (int argc, char *argv[])
 }
 ```
 
-The application will generate the following output:
-
-```bash
-Hello, World!
-```
+The application will return with zero exit code.
 
 ## Step 2. Split engine initialization and script execution
 
@@ -39,6 +35,7 @@ Here we perform the same actions, as `jerry_run_simple`, while splitting into se
 ```c
 #include <string.h>
 #include "jerryscript.h"
+#include "jerryscript-ext/handler.h"
 
 int
 main (int argc, char *argv[])
@@ -49,6 +46,10 @@ main (int argc, char *argv[])
   /* Initialize engine */
   jerry_init (JERRY_INIT_EMPTY);
 
+  /* Register 'print' function from the extensions */
+  jerryx_handler_register_global ((const jerry_char_t *) "print",
+                                  jerryx_handler_print);
+
   /* Setup Global scope code */
   jerry_value_t parsed_code = jerry_parse (script, script_size, false);
 
@@ -78,6 +79,7 @@ Our code is more complex now, but it introduces possibilities to interact with J
 ```c
 #include <string.h>
 #include "jerryscript.h"
+#include "jerryscript-ext/handler.h"
 
 int
 main (int argc, char *argv[])
@@ -88,6 +90,10 @@ main (int argc, char *argv[])
   /* Initialize engine */
   jerry_init (JERRY_INIT_EMPTY);
 
+  /* Register 'print' function from the extensions */
+  jerryx_handler_register_global ((const jerry_char_t *) "print",
+                                  jerryx_handler_print);
+
   jerry_value_t eval_ret;
 
   /* Evaluate script1 */
@@ -120,6 +126,7 @@ This way, we execute two independent script parts in one execution environment.
 ```c
 #include <string.h>
 #include "jerryscript.h"
+#include "jerryscript-ext/handler.h"
 
 int
 main (int argc, char *argv[]) {
@@ -129,6 +136,10 @@ main (int argc, char *argv[]) {
   /* Initializing JavaScript environment */
   jerry_init (JERRY_INIT_EMPTY);
 
+  /* Register 'print' function from the extensions */
+  jerryx_handler_register_global ((const jerry_char_t *) "print",
+                                  jerryx_handler_print);
+
   /* Getting pointer to the Global object */
   jerry_value_t global_object = jerry_get_global_object ();
 
@@ -176,7 +187,6 @@ The following example function will output a JavaScript value:
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-
 #include "jerryscript.h"
 
 static void
@@ -246,8 +256,8 @@ Shell operation can be described with the following loop:
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-
 #include "jerryscript.h"
+#include "jerryscript-ext/handler.h"
 
 static void print_value (const jerry_value_t);
 
@@ -259,6 +269,10 @@ main (int argc, char *argv[])
   /* Initialize engine */
   jerry_init (JERRY_INIT_EMPTY);
 
+  /* Register 'print' function from the extensions */
+  jerryx_handler_register_global ((const jerry_char_t *) "print",
+                                  jerryx_handler_print);
+
   while (!is_done)
   {
     char cmd[256] = {};
@@ -325,6 +339,7 @@ In this example we demonstrate how to use native function and structures in Java
 ```c
 #include <string.h>
 #include "jerryscript.h"
+#include "jerryscript-ext/handler.h"
 
 struct my_struct
 {
@@ -349,6 +364,10 @@ main (int argc, char *argv[])
   /* Initialize engine */
   jerry_init (JERRY_INIT_EMPTY);
 
+  /* Register 'print' function from the extensions */
+  jerryx_handler_register_global ((const jerry_char_t *) "print",
+                                  jerryx_handler_print);
+
   /* Do something with the native object */
   my_struct.msg = "Hello World";
 
@@ -411,6 +430,7 @@ Here we create a JS Object with `jerry_eval`, then extend it with a native funct
 ```c
 #include <string.h>
 #include "jerryscript.h"
+#include "jerryscript-ext/handler.h"
 
 /**
  * Add param to 'this.x'
@@ -451,6 +471,10 @@ main (int argc, char *argv[])
   /* Initialize engine */
   jerry_init (JERRY_INIT_EMPTY);
 
+  /* Register 'print' function from the extensions */
+  jerryx_handler_register_global ((const jerry_char_t *) "print",
+                                  jerryx_handler_print);
+
   /* Create a JS object */
   const jerry_char_t my_js_object[] = " \
     MyObject = \