This is a reorganization of the previous patch contents to cut down on extraneous material. It seems to be complete and could thus be applied to a copy of the newlib-cygwin tree successfully for testing or review.
Methods of testing can be discussed by reply to this post, or on cygwin-developers, whichever is most appropriate. I'm also open to other strategies of implementation if this one seems risky or unattractive for some reason. ..mark [PATCH 1/3] Cygwin: tzcode resync v2: basics [PATCH 2/3] Cygwin: tzcode resync v2: imports [PATCH 3/3] Cygwin: tzcode resync v2: details
