Oversized /var/log/syslog should be aggersively cleaned up to combat login loops

### Problem:
There are many reasons why the syslog file can hyperinflate, not many of which the average user would care about. As you are probably painfully aware, users can easily have it quickly eat up all of their free disk space without them knowing and get them stuck in a login loop.

### Solution:
I suggest the OS should do a periodic check on the syslog file, and delete it if it goes above a few hundred megabytes. This function should work outside of the normal housekeeping function elementary OS has.