Obsolete function. Use curl_easy_unescape(3) instead!
This function will convert the given URL encoded input string to a "plain
string" and return that as a new allocated string. All input characters that
are URL encoded (%XX where XX is a two-digit hexadecimal number) will be
converted to their plain text versions.
If the length argument is set to 0, curl_unescape() will use strlen() on the
input url string to find out the size.
You must curl_free(3) the returned string when youre done with it.