- Copy stable/10@285827 to releng/10.2 in preparation for 10.2-RC1
builds.
- Update newvers.sh to reflect RC1.
- Update __FreeBSD_version to reflect 10.2.
- Update default pkg(8) configuration to use the quarterly branch.[1]

Discussed with: re, portmgr [1]
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

Update this manpage:
- Remove references to cpu_critical_*() as they no longer exist.
- Explain that any preemptions that occur during a critical section are
deferred until the current thread exits the section.
- Remove a bogus example usage of a critical section.
- Note that one can interlock critical sections with spin mutexes in
certain situations.

MFC after: 3 days

Fix the prototypes for cpu_critical_exit and cpu_critical_enter and update
the text to reflect the changes.

Update the header files list.

ispell sweep of share/man/man9/*.

Fully catch up to the recent critical section API change. Update the
content of the manpage and document cpu_critical_enter/exit.

Update function definitions and required include files to reflect
the current state of the system.

Approved by: alfred

mdoc(7) police: Use the new .In macro for #include statements.

mdoc(7) police: there is no single manpage that uses ``.Sy not''.

Add a manpage for the critical_enter/exit() functions.