Incorrect POST implementation in autotagging_calais.module

Hi.

I noticed that long articles weren't having tags generated for them. I checked through with a debugger, and noticed that while the request to OpenCalais was being submitted as a POST, the article content (and other parameters) were being appended to the request URL instead of passed in the POST body.

Since URLs are limited to ~2035 characters, depending on the webserver & browser, articles longer than 2000 or so characters had the request to OpenCalais fail.

This patch places the parameters to OpenCalais in the body of the HTTP request, and should now theoretically work with articles up to OpenCalais' limit of 100,000 characters.