Doc comment maintenance

Fixed doc comments issues:

* Fixed mistyped param doc comments (`/**<` is OK, `/** <` is not).

* Put special characters (e.g., pipe, backslash, etc.) in quotes, as they can
  confuse doxygen and it will print lots of various warnings. For the sake of
  completeness and consistent style, also quote some special characters in
  re-bytecode.h

* Added missing `@{`s, removed extra `@}`s.

* Turned `/*` comments to `/**<` doc comments.

Ensured same style for doc groups everywhere:

* Where `\addtogroup`, `@{`, and `@}` doxygen commands are used, the order to be
  followed is: license, `#ifndef` guards (in headers), includes, `\addtogroup`
  and `@{`, main code content, `@}`, `#endif` guards (in headers).

* Multiple `\addtogroup`s or multiple `@}`s should be in the same doc comment.

* First `\addtogroup` should be on the very first line of a doc comment, i.e.,
  `/** \addtogroup`.

JerryScript-DCO-1.0-Signed-off-by: Akos Kiss akiss@inf.u-szeged.hu

jerry-core/ecma/builtin-objects/ecma-builtin-helpers-json.c

@@ -1,4 +1,4 @@
-/* Copyright 2014-2015 Samsung Electronics Co., Ltd.
+/* Copyright 2014-2016 Samsung Electronics Co., Ltd.
  * Copyright 2015-2016 University of Szeged.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
@@ -14,6 +14,11 @@
  * limitations under the License.
  */
 
+#include "ecma-alloc.h"
+#include "ecma-helpers.h"
+#include "ecma-builtin-helpers.h"
+#include "lit-char-helpers.h"
+
 /** \addtogroup ecma ECMA
  * @{
  *
@@ -21,11 +26,6 @@
  * @{
  */
 
-#include "ecma-alloc.h"
-#include "ecma-helpers.h"
-#include "ecma-builtin-helpers.h"
-#include "lit-char-helpers.h"
-
 /**
  * Check the object value existance in the collection.
  *

jerry-core/ecma/builtin-objects/ecma-builtin-helpers.c

@@ -123,7 +123,7 @@ ecma_builtin_helper_object_to_string (const ecma_value_t this_arg) /**< this arg
  */
 ecma_value_t
 ecma_builtin_helper_get_to_locale_string_at_index (ecma_object_t *obj_p, /**< this object */
-                                                   uint32_t index) /** <array index */
+                                                   uint32_t index) /**< array index */
 {
   ecma_value_t ret_value = ecma_make_simple_value (ECMA_SIMPLE_VALUE_EMPTY);
   ecma_string_t *index_string_p = ecma_new_ecma_string_from_uint32 (index);