Wider protection of article currently being read.

See @marchyman comment in issue #129 : <https://github.com/ViennaRSS/vienna-rss/issues/129#issuecomment-11984709>
Be tolerant with feed elements which contain XML/XHTML while they shouldn't : example reported by "two bottles" at <http://forums.cocoaforge.com/viewtopic.php?t=25590&p=135595>

Note : we should revisit all this code more in depth, as it uses many methods which are declared deprecated starting from OS X v10.8
Merge pull request #133 from barijaona/XMLparsing

Be tolerant with feed elements which contain XML/XHTML while they shouldn't
Merge pull request #131 from barijaona/refreshes-no-annoyance

Wider protection of article currently being read.