Backport: email cloaking does not work with & in text to 2.5.x

Please see the orginal issue for 3.x (https://github.com/joomla/joomla-cms/issues/4263) and the PR (https://github.com/joomla/joomla-cms/pull/4273)

The same issue is in 2.5.x and the same fix work good for me.

Sinze the code is not from me i mark the first successful test.