Issue #2763 - Fixes Session GC Probability Calculation

This should resolve issue #2763 where the cookie session garbage
collection was running every request.
Merge pull request #2764 from refringe/feature/cookie_session

Issue #2763 - Fixes Session GC Probability Calculation
DB call_function() bug : funny typo -or- smart autocomplete?
Merge pull request #2770 from kakysha/themostawesomebranchevercreatedforcodeigniter

DB call_function() bug : funny typo -or- smart autocomplete?