[tz] Fractional seconds in zic input

[Paul Eggert]

On 02/05/2018 04:55 AM, Howard Hinnant wrote:
> 2.  Doing this without specifying a maximum precision will mean the substantial breakage I speak of in 1) will happen every time the precision is increased.
What sort of breakage do you see? Is the problem that different 
downstream users will compare calculations and disagree about the exact 
results because they use differing precisions? But we already have that 
problem, as at least one downstream user already discards sub-minute 
information, namely Kerry Shetline's recently-discussed tzdata compressor.