tramp (2.2.13.25.2); setting GZIP environment variable breaks tramp

[Francesco Potortì]

Recently gzip started to emit a warning (on stderr, I believe) saying
that setting the GZIP env var is deprecated.

I never cared too much about it until tramp stopped working.  After some
time, I discovered that GZIP was the culprit.

For example, both with the ssh and scp methods, reading a remote file
works, but writing it back after modification fails.

Maybe tramp could detect GZIP's warning and dtrt