Invalid html used to generate PDF resulting in rendering problems

When generating PDF (e.g. Contribution Receipt), there appears the following line on each page:
xmlns="http://www.w3.org/1999/xhtml">
Furthermore special characters like german umlauts are not encoded properly.

see: http://forum.civicrm.org/index.php/topic,14957.0.html

In the function domlib($text, $fileName) located in CRM/Utils/PDF/Utils.php html tags are partially stripped out of the message template to avoid them appearing multiple times if more then one record is printed. The <html> tag is not stripped out thus the appearing of above line on every page.
In order to solve the problem with the encoding of special characters the html passed to dompdf should be valid and specify UTF-8 as charset (see attached patch file)