Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

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

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

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

Hide the implementation details about multiple threading libraries
from the synopses of pthread*(3) manpages.

Reviewed by: deischen, davidxu

o Add pthread_yield.3 man page.

PR: docs/100083
Reviewed by: deischen, ru
Obtained from: OpenBSD
MFC after: 2 weeks