Description:
------------
If dbase_open() fails due to an unsupported field type, it leaks the
memory of the strdup()'d names of previous supported fields.


Test script:
---------------
<?php

$filename = __DIR__ . DIRECTORY_SEPARATOR . 'test.dbf';

$db = dbase_create($filename, [['foo', 'C', 1], ['bar', 'C', 1]]);
dbase_close($db);

$file = fopen($filename, 'r+b');
fseek($file, 75); // offset of the type marker of the second field
fwrite($file, 'Y'); // 'Y' is unsupported
fclose($file);

dbase_open($filename, 0);


Expected result:
----------------
valgrind is happy

Actual result:
--------------
valgrind reports a memory leak