Version of clamdrib compatible with recent Thunderbird versions

The version of clamdrib earlier available from addons.mozilla.org was not compatible with Thunderbird 3.0b3 and later versions even when the version range in install.rdf is editted. It worked with some of 3.0b3pre though.

Here is updated version that seems to work also with recent thunderbird versions (last checked with 17.0.4).

Andris Pavenis <andris.paveni at iki.fi>