Serbian translation updated by Miodrag Milic (#12800)

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@11160 e93f8b46-1217-0410-a6f0-8f06a7374b81
Serbian translation changed by Miodrag Milic (#12806, #12800)

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@11161 e93f8b46-1217-0410-a6f0-8f06a7374b81