To record discussion with Stefan regarding 64-bit time_t

To remember:

signed   32-bit time_t will overflow in 2038 (soon enough)
unsigned 32-bit time_t will overflow in 2106 ("not my problem")

https://en.wikipedia.org/wiki/Year_2038_problem
https://wiki.debian.org/ReleaseGoals/64bit-time

64-bit Linux uses 64-bit time_t since as far back as el6.

MIDAS uses unsigned 32-bit (DWORD) time-in-seconds in many places (ODB, event 
headers, event buffers, etc)

MIDAS also uses unsigned 32-bit (DWORD) time-in-milliseconds in many places.

All time arithmetic is done using unsigned 32-bit math, these time calculations
are good until year 2106, at which time they will wrap around
(but still work correctly).

So we do not need to do anything, but...

To reduce confusion between the different time types, we will probably
introduce a 32-bit-time-in-seconds data type (i.e. time32_t alias for uint32_t),
and a 32-bit-time-in-milliseconds data type (i.e. millitime32_t alias for 
uint32_t). Also rename ss_time() to ss_time32() and ss_millitime() to 
ss_millitime32().

This should help avoiding accidental mixing of MIDAS 32-bit time, system 64-bit 
time and MIDAS 32-bit-time-in-milliseconds.

(confusion between time-in-seconds and time-in-milliseconds happened several 
times in MIDAS code).

There will be additional discussion and announcements if we go ahead with these 
changes.

K.O.