smr.inc: simplify format_time
smr.inc: simplify format_time

Loop over an array of time units instead of repeating the same
processing for each unit.

To my chagrin, we omit the Oxford comma when stringifying the time,
because it is algorithmically simpler.

hemberger/smr,hemberger/smr,hemberger/smr,smrealms/smr,hemberger/smr,smrealms/smr,smrealms/smr