Resolves #56045: Add random variable in captcha image src

git-svn-id: https://svn.typo3.org/TYPO3v4/Extensions/sr_freecap/trunk@83922 735d13b6-9817-0410-8766-e36946ffe9aa
Update version to 2.0.8

git-svn-id: https://svn.typo3.org/TYPO3v4/Extensions/sr_freecap/trunk@83923 735d13b6-9817-0410-8766-e36946ffe9aa