do not delegate cleanup to callers but enforce it here as well, thanks Martín for suggestion

git-svn-id: http://dev.piwik.org/svn/trunk@7779 59fd770c-687e-43c8-a1e3-f5a4ff64c105
Avoid http header injection

git-svn-id: http://dev.piwik.org/svn/trunk@7780 59fd770c-687e-43c8-a1e3-f5a4ff64c105