Log Message:
Initial import of libtai 0.60, a public-domain library for storing
and manipulating dates and times.

libtai supports two time scales: (1) TAI64, covering a few hundred
billion years with 1-second precision; (2) TAI64NA, covering the
same period with 1-attosecond precision. Both scales are defined
in terms of TAI, the current international real time standard.

libtai provides an internal format for TAI64, struct tai, designed
for fast time manipulations. The tai_pack() and tai_unpack() routines
convert between struct tai and a portable 8-byte TAI64 storage
format. libtai provides similar internal and external formats for
TAI64NA.

This version of libtai requires a UNIX system with gettimeofday().
It will be easy to port to other operating systems with compilers
supporting 64-bit arithmetic.