Explain config_line_find() behavior on duplicates.

  (*lst) = newline;

}

/** Return the line in <b>lines</b> whose key is exactly <b>key</b>, or NULL

 * if no such key exists. For handling commandline-only options only; other

 * options should be looked up in the appropriate data structure. */

/** Return the first line in <b>lines</b> whose key is exactly <b>key</b>, or

 * NULL if no such key exists.

 *

 * (In options parsing, this is for handling commandline-only options only;

 * other options should be looked up in the appropriate data structure.) */

const config_line_t *

config_line_find(const config_line_t *lines,

                 const char *key)