Copy stable/11@r303970 to releng/11.0 as part of the 11.0-RELEASE
cycle.

Prune svn:mergeinfo from the new branch, and rename it to RC1.

Update __FreeBSD_version.

Use the quarterly branch for the default FreeBSD.conf pkg(8) repo and
the dvd1.iso packages population.

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

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

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

Improve errno documentation in pthread_create(3) and thr_new(2)

Add some missing errno values to thr_new(2) and pthread_create(3).
In particular, EDEADLK was not documented in the latter.
While I'm here, improve some English and cross-references.

Reviewed by: kib
Sponsored by: Dell Inc.
Differential Revision: https://reviews.freebsd.org/D6663

thr_*(2): Add xrefs to what libthr implements using each syscall.

Add text to thr_exit(2) and thr_new(2) discouraging their use in
applications since calling these in a process with libthr loaded will
confuse libthr and is likely to cause hangs or crashes.

The thr_kill2(2) call is not used by libthr and may be useful in special
applications.

The other calls can be used in applications but it should not be necessary.

_umtx_op(2),thr_*(2): Various spelling, grammar and mdoc fixes.

Document the non-obsoleted kernel interfaces used by libthr.

Reviewed by: emaste
Sponsored by: The FreeBSD Foundation
Differential revision: https://reviews.freebsd.org/D6335