2038 ( Y2K38 ) bug with expiration dates

Reproduce
1. Assign a uc_roles role expiration date for January 18, 2038.
2. Trigger role renewal.

Symptom
Instead of resetting the expiration date to the appropriate date in the future, it gets reset to 0 ("zero").
Once the expiry is set to a date in the past, the role will expire immediately on the next cron run.

Solution
There are already at least a couple issues dealing with the Year 2038 problem.
Seeing as how UC 6.x will likely never be updated to benefit from these patches, an interim solution is to not try and set the expiry to a value greater than 2147483647.