Tweak gnutls-peer-status reporting

* src/gnutls.c (Fgnutls_peer_status): Report :compression and
:encrypt-then-mac only if the underlying GnuTLS library has
the corresponding features.  This give the Elisp caller a bit
more information about the peer status.
* lisp/net/nsm.el (nsm-protocol-check--compression):
Don’t worry about compression in newer GnuTLS versions
that do not support compression.
1 job for master in 64 minutes and 19 seconds (queued for 4 seconds)
Status Job ID Name Coverage
  Test
failed #3112
test-all

01:04:19

 
Name Stage Failure
failed
test-all Test
Makefile:318: recipe for target 'check-doit' failed
make[2]: *** [check-doit] Error 1
make[2]: Leaving directory '/builds/emacs/emacs/test'
Makefile:293: recipe for target 'check-expensive' failed
make[1]: *** [check-expensive] Error 2
make[1]: Leaving directory '/builds/emacs/emacs/test'
Makefile:959: recipe for target 'check-expensive' failed
make: *** [check-expensive] Error 2
ERROR: Job failed: exit code 1