Make logging an optional feature and disable it by default (#2449)

JerryScript-DCO-1.0-Signed-off-by: Akos Kiss akiss@inf.u-szeged.hu

docs/02.API-REFERENCE.md

@@ -60,6 +60,7 @@ Possible compile time enabled feature types:
  - JERRY_FEATURE_DATE - Date support
  - JERRY_FEATURE_REGEXP - RegExp support
  - JERRY_FEATURE_LINE_INFO - line info available
+ - JERRY_FEATURE_LOGGING - logging
 
 ## jerry_parse_opts_t
 

docs/05.PORT-API.md

@@ -63,6 +63,11 @@ typedef enum
  *
  * Example: a libc-based port may implement this with vfprintf(stderr) or
  * vfprintf(logfile), or both, depending on log level.
+ *
+ * Note:
+ *      This port function is called by jerry-core when JERRY_ENABLE_LOGGING is
+ *      defined. It is also common practice though to use this function in
+ *      application code.
  */
 void jerry_port_log (jerry_log_level_t level, const char *fmt, ...);
 ```