eina_lock: add since tag to now exposed eina_lock_debug API

This function was static inline before but form 1.19 onwards its EAPI so give
it a since tag.

src/lib/eina/eina_lock.h

@@ -210,6 +210,8 @@ static inline Eina_Lock_Result eina_lock_release(Eina_Lock *mutex);
  *          lock state, thread number and a backtrace.
  *
  * @note If @c EINA_HAVE_DEBUG_THREADS is not defined, this function does nothing.
+ *
+ * @since 1.19
  */
 EAPI void eina_lock_debug(const Eina_Lock *mutex);