Proposed patch to sync tz from upstream

[Roland McGrath]

That needs to be multiple separate changes.

The tzcode updates need to reviewed individually like any other code changes.
Heretofore we have always updated to a particular tzcode YYYYL release and
descirbed it as such.  I don't think we want to stray from that policy
unless they have stopped making such releases.

The page at https://sourceware.org/glibc/wiki/SharedSourceFiles does not
talk about tzcode, but should.  Can you add something there?

We have stopped updating tzdata just to update it, because we no longer
install any tzdata for 'make install', nor expect anyone to use the tzdata
source files in our source tree.  We have them there solely for the testing
we do in timezone/Makefile.  A good first change would be the one that just
removes everything from tzdata that we are not actually using.  After that,
and update of the few files we do use would be fine.


Thanks,
Roland