time: read 64-bit data if available

Also store 64-bit data in lib/time/zoneinfo.zip.

The comments argue that we don't need the 64-bit data until 2037 or
2106, but that turns out not to be the case. We also need them for
dates before December 13, 1901, which is time.Unix(-0x80000000, 0).

Fixes #30099

Change-Id: Ib8c9efb29b7b3c08531ae69912c588209d6320e9
Reviewed-on: https://go-review.googlesource.com/c/161202


Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>