Re-target for ES.Next (#3901)

A list of changes:
- 'es2015-subset' profile is deprecated, and an 'es.next' profile is added.
- The default profile is changed to 'es.next'
- Renamed the JERRY_ES2015 guard to JERRY_ESNEXT
- Renamed JERRY_ES2015_BUILTIN_* guards to JERRY_BUILTIN_*
- Moved es2015 specific tests to a new 'es.next' subdirectory
- Updated docs, targets, and test runners to reflect these changes

Resolves #3737.

JerryScript-DCO-1.0-Signed-off-by: Dániel Bátyai dbatyai@inf.u-szeged.hu

jerry-core/ecma/operations/ecma-symbol-object.h

@@ -16,7 +16,7 @@
 #ifndef ECMA_SYMBOL_H
 #define ECMA_SYMBOL_H
 
-#if ENABLED (JERRY_ES2015)
+#if ENABLED (JERRY_ESNEXT)
 #include "ecma-globals.h"
 
 /** \addtogroup ecma ECMA
@@ -44,7 +44,7 @@ ecma_symbol_to_string_helper (ecma_value_t this_arg, bool is_to_string);
 ecma_value_t
 ecma_get_symbol_descriptive_string (ecma_value_t symbol_value);
 
-#endif /* ENABLED (JERRY_ES2015) */
+#endif /* ENABLED (JERRY_ESNEXT) */
 /**
  * @}
  * @}