Implement direct strings. (#2196)

Direct strings are a new type of direct ecma-values (no memory allocation
is needed for encoding them) in JerryScript. Currently magic strings,
external magic strings and uint values are encoded as direct strings.

The constant pool of JerryScript byte-code is changed to hold ecma-values
rather than cpointers to support direct strings.

JerryScript-DCO-1.0-Signed-off-by: Zoltan Herczeg zherczeg.u-szeged@partner.samsung.com

jerry-core/parser/regexp/re-bytecode.h

@@ -85,7 +85,7 @@ typedef enum
 typedef struct
 {
   ecma_compiled_code_t header;       /**< compiled code header */
-  jmem_cpointer_t pattern_cp;        /**< original RegExp pattern */
+  ecma_value_t pattern;              /**< original RegExp pattern */
   uint32_t num_of_captures;          /**< number of capturing brackets */
   uint32_t num_of_non_captures;      /**< number of non capturing brackets */
 } re_compiled_code_t;