Implement the Symbol builtin object (#2601)

This patch contains the base functionalities that the new builtin object requires.

Currently unavailable:
 - print (Symbol('foo')) - this features requires the refactor of the print handler function
 - Several global symbol based builtin routines (follow up patch)

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

jerry-core/ecma/builtin-objects/ecma-builtin-global.inc.h

@@ -205,6 +205,13 @@ OBJECT_VALUE (LIT_MAGIC_STRING_MAP_UL,
               ECMA_PROPERTY_CONFIGURABLE_WRITABLE)
 #endif /* !CONFIG_DISABLE_ES2015_MAP_BUILTIN */
 
+#ifndef CONFIG_DISABLE_ES2015_SYMBOL_BUILTIN
+/* ECMA-262 v6, 19.4.1.1 */
+OBJECT_VALUE (LIT_MAGIC_STRING_SYMBOL_UL,
+              ECMA_BUILTIN_ID_SYMBOL,
+              ECMA_PROPERTY_CONFIGURABLE_WRITABLE)
+#endif /* !CONFIG_DISABLE_ES2015_SYMBOL_BUILTIN */
+
 /* Routine properties:
  *  (property name, C routine name, arguments number or NON_FIXED, value of the routine's length property) */