In a number of locations in the code, there were conversions of message
expiration times from seconds to milliseconds, and then assigned to `long`
contexts. However these conversions were being done as integer multiplication
rather than long multiplication, meaning that there was a potential for
overflows.
Specifically, the maximum value that could be represented before overflowing
was (2^31 / 1000 / 60 / 60 / 24) days = 24.8 days (< 1 month). Luckily the
current allowed timeouts are all less than that value, but this fix would
remove the artificial restriction, effectively allowing values of 1000x greater
(68 years), at least for android.
Related #5775Closes#7338
