Don't map imaps to 993 anymore except on old Windows versions

'open-network-stream' will do the imaps service lookup itself, and
using 993 forced the user to use the numeric value in .authinfo for
certificate lookups.

* lisp/gnus/nnimap.el (nnimap-map-port): Only do mapping for Windows
XP or earlier.
* etc/NEWS: Describe imaps mapping change.
1 job for master in 57 minutes and 54 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Test
failed #736
test-all

00:57:54

 
Name Stage Failure
failed
test-all Test
make[2]: *** [check-doit] Error 1
Makefile:309: recipe for target 'check-doit' failed
make[2]: Leaving directory '/builds/emacs/emacs/test'
Makefile:284: recipe for target 'check-expensive' failed
make[1]: *** [check-expensive] Error 2
make[1]: Leaving directory '/builds/emacs/emacs/test'
Makefile:962: recipe for target 'check-expensive' failed
make: *** [check-expensive] Error 2
ERROR: Job failed: exit code 1