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: r264384, r264415mdoc and language improvements.
MFC r228741, r228742:Add timecounters(4) man page alike to eventtimers(4).
Add timecounters(4) man page alike to eventtimers(4).