Fix links to PHP PDO drivers manual

installer/check.php

@@ -64,12 +64,12 @@ $source_urls = array(
     'Intl'      => 'http://www.php.net/manual/en/book.intl.php',
     'Exif'      => 'http://www.php.net/manual/en/book.exif.php',
     'PDO'       => 'http://www.php.net/manual/en/book.pdo.php',
-    'pdo_mysql'   => 'http://www.php.net/manual/en/book.pdo-mysql.php',
-    'pdo_pgsql'   => 'http://www.php.net/manual/en/book.pdo-pgsql.php',
-    'pdo_sqlite'  => 'http://www.php.net/manual/en/book.pdo-sqlite.php',
-    'pdo_sqlite2' => 'http://www.php.net/manual/en/book.pdo-sqlite.php',
-    'pdo_sqlsrv'  => 'http://www.php.net/manual/en/book.pdo-sqlsrv.php',
-    'pdo_dblib'   => 'http://www.php.net/manual/en/book.pdo-dblib.php',
+    'pdo_mysql'   => 'http://www.php.net/manual/en/ref.pdo-mysql.php',
+    'pdo_pgsql'   => 'http://www.php.net/manual/en/ref.pdo-pgsql.php',
+    'pdo_sqlite'  => 'http://www.php.net/manual/en/ref.pdo-sqlite.php',
+    'pdo_sqlite2' => 'http://www.php.net/manual/en/ref.pdo-sqlite.php',
+    'pdo_sqlsrv'  => 'http://www.php.net/manual/en/ref.pdo-sqlsrv.php',
+    'pdo_dblib'   => 'http://www.php.net/manual/en/ref.pdo-dblib.php',
     'PEAR'      => 'http://pear.php.net',
     'Net_SMTP'  => 'http://pear.php.net/package/Net_SMTP',
     'Mail_mime' => 'http://pear.php.net/package/Mail_mime',