Reimplement the `fill-flowed' function to respect space stuffing

* lisp/mail/flow-fill.el (fill-flowed): Reimplement the function
to respect space-stuffing (bug#17190).

* test/lisp/mail/flow-fill-tests.el
(fill-flow-tests-fill-flowed-stuffed): New test.
(fill-flow-tests-fill-flowed-decode): Rename the test so that it
actually runs.
1 job for master in 60 minutes and 26 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Test
failed #2996
test-all

01:00:26

 
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