replace preg_replace /e with preg_replace_callback

uses `create_function` to support both PHP 5.2 and PHP 5.5
`create_function` uses `eval` internally so probably it's
better to have this fix only for Kohana v.3.2

Thank you @Zeelot for the help
Merge pull request #465 from enov/4819/preg_replace-e-preg_replace_callback

Fixes #4819: Replace preg_replace /e with preg_replace_callback