char *curl_unescape( const char *url, int length );
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 you're done with it.