TYPO3 Core

when you configure the Filebackend in windows with absolute path, example:
array('cacheDirectory' => 'C:/xampp/htdocs/tv/t3cache/')

you will get an exeption that the path 'C:/xampp/htdocs/tv/t3cache/' doesn't exists.
I wondered, the path is correct and folder exist, but the FileBackend checks for '/' as first char for absolute path, and if not the path is concatenated with PATH_site.

So following is needed:
1) if on windows do a different check for absolute path
2) if the dir doesn't exist, print in exceptionthe path from the check (in this case PATH_site . configuredPath)

(issue imported from #M13925)