What steps will reproduce the problem? 1. Index a document containing at least one control character

What is the expected output? What do you see instead? Document fails to index at solr and a XML parsing exception will occur.

I attached a patch to solve this issue.

For the Drupal module, we are applying this regex to all fields - otherwise we frequently see encoding issues.

Note - that as the author of those comments and code which are from the Drupal module, I'm happy to release them for inclusion here under the BSD license.

Patch (with minor changes) has been applied in r14