Hotfix/3376

This PR addresses #3376 which notes that we had a number of locations that were still using the `/e` modifier to `preg_replace`, which has been marked deprecated in PHP 5.5, and which is a bad practice anyways.

I found two locations where this was happening:

- `Zend\Filter\Word\SeparatorToCamelCase`, which most other Word filters inherit from, was setting a PCRE pattern that used the "e" modifier. I modified the filter to no longer call on `parent::filter`, and instead call `preg_replace_callback`; the eval expressions were converted to closures, and the "e" modifier removed.
- `Zend\Ldap\Converter\Converter` was using the "e" modifier; I modified the code to remove this, and instead call `preg_replace_callback` with a closure for the replacement.

At this point, all tests are now running for me on 5.5.0alpha3; once merged, I'll provide an additional PR adding 5.5 to our travis builds.