fix incorrect contact; closes PR 14798

please include in the 6.1.1 release

(cherry picked from commit 86017992ab840e81f63742a1a0505bb47fd22abe)
work around a kqueue bug(?) on Mac OS X

There seems to be a problem in kqueue() on Mac OS X for watching for
FIFO write availability, where adding a read event for the same FIFO
(at a different file descritor) can disable the write event.

Merge to v6.1.1

(cherry picked from commit a352470914661b79a04946a585e1859addbbe208)
make `read-line` interruptable on a primitive port

Closes PR 14800

Merge to v6.1.1

(cherry picked from commit f31c6563e42c5bfb52f2ed5e6fcb5549f6aadeeb)
fix a contract example in the documentation

closes PR 14798 (the previous commit, 86017992ab, that
claimed to fix this PR is unrelated; sorry for that)

Please include in 6.1.1

(cherry picked from commit df8fef86da949ef883125855aa0ea1b23c635c0e)