Adjust composer autoload paths in bin

It looks like this code was lifted from PHPUnit, which places the
binary in the root directory, rather than bin/, which is why we
need one more level of ../ everywhere to make things work.

bin/phpyacc

@@ -4,7 +4,7 @@ namespace PhpYacc;
 
 use PhpYacc\Grammar\Context;
 
-foreach (array(__DIR__ . '/../../autoload.php', __DIR__ . '/../vendor/autoload.php', __DIR__ . '/vendor/autoload.php') as $file) {
+foreach (array(__DIR__ . '/../../../autoload.php', __DIR__ . '/../../vendor/autoload.php', __DIR__ . '/../vendor/autoload.php') as $file) {
     if (file_exists($file)) {
         define('COMPOSER_INSTALL', $file);