* lisp/mail/flow-fill.el (fill-flowed): Loop until all flowed lines
are collected.
* test/lisp/mail/flow-fill-tests.el
(fill-flow-tests-fill-flowed-decode): Also test for multiple
flowed lines (bug#42855).
* 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.