Output of description and dc.description is not properly sanitized

Hi,

when meta tag content is automatically generated from the node content, the output is not properly sanitized, because markup from the node's textfields is being inserted into the <meta name="description"... and <meta name="dc.description"... fields.

Configuration from ./admin/content/nodewords:

• "Generate meta tag content when the meta tag content is empty"
• Generation source: "Generate meta tags content from the node teaser"

Steps to reproduce: Install a 3rd party input filter from contrib, e.g. mediawiki_filter and configure nodewords as described above. You'll see that output like this in the generated HTML code:

<meta name="description" content="&#039;&#039;&#039;A famous name&#039;&#039;&#039; from Czech Republic is &#039;&#039;&#039;doing an excellent job&#039;&#039;&#039; in &#039;&#039;&#039;healthcare&#039;&#039;&#039; for the &#039;&#039;&#039;[[United Nations]]&#039;&#039;&#039;." />

''' is the Mediawiki markup ('''...''') in Unicode entities for <bold>. Mediawiki style links ([[...]]) are not interpreted at all. It's similar for the <meta name="dc.description"... meta tag, if used.

I don't know if this is intended behaviour, but as it is, the output is useless as a meta tag. I'd think that the content from the node body would have to run through the input filter first to become proper HTML, and then all HTML tags would have to be stripped before the metatag token is inserted into the header of the resulting HTML page.

Thanks & greetings, -asb