add connect error handling

pg4wp/core.php

@@ -24,6 +24,7 @@ $replaces = array(
     'new wpdb'	=> 'new wpdb2',
     'instanceof mysqli_result' => 'instanceof \PgSql\Result',
     'instanceof mysqli' => 'instanceof \PgSql\Connection',
+    '$this->dbh->connect_errno' => 'wpsqli_connect_error()',
     'mysqli_'	=> 'wpsqli_',
     'is_resource'	=> 'wpsqli_is_resource',
     '<?php'		=> '',