typo (re-apply correction of r756, accidentally reverted in r763)

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/surveillance@765 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Corrects a bug in farringtonFlexible.r (in case of multivariate time series)

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/surveillance@766 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Corrects another bug in farringtonFlexible.r (alarms when observed AND upperbound are 0 -> did not make sense)

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/surveillance@767 edb9625f-4e0d-4859-8d74-9fd3b1da38cb