Implement ES2015 class feature (part II.) (#2439)

This patch is the second milestone of the implementation of this new language element.

Supported:
 - Single class inheritance
 - Functionality of 'super' keyword
 - Implicit constructor in class heritage
 - Specific behaviour while extending with the built-in 'Array' or '%TypedArray%' object
 - Abstract subclasses (Mix-ins)

JerryScript-DCO-1.0-Signed-off-by: Robert Fancsik frobert@inf.u-szeged.hu

jerry-core/jcontext/jcontext.h

@@ -109,7 +109,7 @@ struct jerry_context_t
   ecma_value_t error_value; /**< currently thrown error value */
   uint32_t lit_magic_string_ex_count; /**< external magic strings count */
   uint32_t jerry_init_flags; /**< run-time configuration flags */
-  uint32_t status_flags; /**< run-time flags */
+  uint32_t status_flags; /**< run-time flags (the top 8 bits are used for passing class parsing options) */
 
 #ifndef CONFIG_ECMA_PROPERTY_HASHMAP_DISABLE
   uint8_t ecma_prop_hashmap_alloc_state; /**< property hashmap allocation state: 0-4,