fixed preg_replace deprecated error in PHP 5.5

classes/database/connection.php

@@ -635,8 +635,10 @@ public function quote_identifier($value)

		if (strpos($value, '"') !== false)
		{
			// required for PHP 5.5- (no access to $this in closure)
			$that = $this;
			// Quote the column in FUNC("ident") identifiers
			return preg_replace('/"(.+?)"/e', '$this->quote_identifier("$1")', $value);
			return preg_replace_callback('/"(.+?)"/', function ($matches) use($that) { return $that->quote_identifier($matches[1]); }, $value);
		}
		elseif (preg_match("/^'(.*)?'$/", $value))
		{