Fixed bug #12232: [Performance] md5_file() to check if a file has been changed...

Fixed bug #12232: [Performance] md5_file() to check if a file has been changed is very expensive (Thanks to André Stösel and Vladimir Podkovanov)

git-svn-id: https://svn.typo3.org/TYPO3v4/Core/trunk@10126 709f56b5-9817-0410-a4d7-c38de5d9e867