64-bit work

[Olson, Arthur David (NIH/NCI)]

Since the 5-byte (rather than 8-byte) extension to the time zone binary data
file format went over with an overwhelming thud, my current thinking is to
stick revert to the 8-byte approach.

The name of the game would be to produce binary files with:
	1. data with 32-bit time values through 2037 (for use by old
systems)
	2. data with 64-bit time values for "historic" years
	3. a newline enclosed, POSIX-conforming
TZ-environment-variable-style string
	   telling what to do in years beyond those covered by 2 above.

There are a few places (Cairo, Godthab, Chile) that can't be represented by
POSIX-conforming strings; for these we'd punt to the "write 400 years worth
of data and work modulo 400" approach (leaving off the trailing TZ string).

				--ado