My brief reading tells me that cron.allow and cron.deny are optional files, usually located in /etc. Without them only the root user may setup crontabs affecting system files. Individual users may still setup crontabs for their own (non-system) files.
To verify whether or not you have cron installed, from the command-line, run 'locate cron' (without quotes). If cron is installed, you will see output showing where the various files are located.