Fix tests

There are several tests which fail on windows due to cross platform issues (line endings and directory separators). 
Here's the tracker: http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=32842&start=0

In case of line endings, where appropriate, I've changed the test to use `\n` instead of `PHP_EOL`. 
In case of directory separators, `JPath::clean()` will have already changed everything to `DIRECTORY_SEPARATOR` by the time the test runs so, I've changed the test to also use that instead of `/`. 
In a case where we are just testing an xml string, I've changed the test itself to `assertXmlStringEqualsXmlString` so that line ending issues are not even considered at all. 

There are still some tests failing in `JViewLegacyTest` but, in my opinion, these are actually problems with `JViewLegacy` and not the test. Basically, it should be calling `JPath::clean()` on directory strings but it isn't. So I will include those fixes in a different PR.