URLConnection.guessContentTypeFromStream() does not support UTF8 and UTF32 with BOM

[Chris Hegarty]

Charles, Alan,

I filed CR 7026346: " URLConnection.guessContentTypeFromStream does not 
support UTF-8 and UTF-32 xml streams with BOM", for this issue.

I also creating a webrev from your patch, with the following changes:

  * Moved the UTF-32BE before the UTF-32LE, as per the comment
  * filled out the UTF-32BE and UTF-32LE around the '?' '<' 'x' chars
  * Included you original test in an existing test for xml content types.

Charles, Please verify the changes.

http://cr.openjdk.java.net/~chegar/7026346/webrev.00/webrev/

Alan,
  I believe you already looked at the original patch. I think these 
changes are fine, can you please also review.

Thanks,
-Chris.