script: Correct -F in man page and usage string.
Sponsored by: Klara, Inc.
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D37138
(cherry picked from commit 8e096e24d4344b6d3d16e24d58d5d8a0fa9733c9)
script: Add usage string for playback mode.
Sponsored by: Klara, Inc.
Differential Revision: https://reviews.freebsd.org/D37138
(cherry picked from commit e7c13cf4383d8216149becf7f843a2e00b30d2e2)
script: Use size_t / ssize_t where needed.
Sponsored by: Klara, Inc.
Differential Revision: https://reviews.freebsd.org/D37177
(cherry picked from commit 3276866f40caaf3d5605d5695f460cbdf035ef45)
script: Further usage string nits.
Sponsored by: Klara, Inc.
Differential Revision: https://reviews.freebsd.org/D37177
(cherry picked from commit 6ac087cf8ff4de22dc0b1b7ce1248f0a1558ddc2)
script: Handle a missing 's' stamp gracefully.
Sponsored by: Klara, Inc.
Differential Revision: https://reviews.freebsd.org/D37182
(cherry picked from commit 473e9fcab4ea9379f53e1f7d8e41f5a5754d0007)