Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFC r233648:
Remove trailing whitespace per mdoc lint warning

Approved by: cperciva (implicit)

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Fix a whitespace nit.

MFC after: 1 week
X-MFC with: r216995

Add a man page for the Object Specific Data (OSD) KPI.

Although not directly related the FreeBSD Foundation funded "Five New TCP
Congestion Control Algorithms for FreeBSD" project, the understanding and
inspiration required to write this documentation was significantly bolstered
by the Foundation's support.

Reviewed by: pjd
MFC after: 1 week