Improve the evaluate requests (#2583)

Currently it evaluates the given expression in the context of the top most stack frame.
The expression should access to any variables and arguments that are in the scope chain.
Implement the eval_at request with the level of the scope chain as a further argument.

JerryScript-DCO-1.0-Signed-off-by: Robert Sipka rsipka.uszeged@partner.samsung.com

jerry-core/ecma/base/ecma-globals.h

@@ -80,10 +80,18 @@ typedef enum
   ECMA_TYPE___MAX = ECMA_TYPE_ERROR /** highest value for ecma types */
 } ecma_type_t;
 
+#ifdef JERRY_DEBUGGER
+/**
+ * Shift for scope chain index part in ecma_parse_opts
+ */
+#define ECMA_PARSE_CHAIN_INDEX_SHIFT 16
+#endif
+
 /**
  * Option flags for script parsing.
  * Note:
  *      The enum members must be kept in sync with parser_general_flags_t
+ *      The last 16 bits are reserved for scope chain index
  */
 typedef enum
 {