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

libcuse: make more use of the howmany() macro when available.

We have a howmany() macro in the <sys/param.h> header that is
convenient to re-use as it makes things easier to read.

Make CUSE usable with platforms where the size of "unsigned long" is
different from the size of a pointer.

Fix compiler locking diagnostic warnings.

PR: 194289

Add lock annotations to libcuse.

- Add annotations to the lock/unlock function to indicate that the
function is allowed to lock and unlock the underlying pthread mutex.

- Add __guarded_by() annotations to the global variables.

Approved by: hselasky@

Fix destruction of character devices by passing correct pointer to
kernel in IOCTL request.

Submitted by: Andrey Zholos <aaz@q-fu.com>

Initial import of character device in userspace support for FreeBSD.
The CUSE library is a wrapper for the devfs kernel functionality which
is exposed through /dev/cuse . In order to function the CUSE kernel
code must either be enabled in the kernel configuration file or loaded
separately as a module. Currently none of the committed items are
connected to the default builds, except for installing the needed
header files. The CUSE code will be connected to the default world and
kernel builds in a follow-up commit.

The CUSE module was written by Hans Petter Selasky, somewhat inspired
by similar functionality found in FUSE. The CUSE library can be used
for many purposes. Currently CUSE is used when running Linux kernel
drivers in user-space, which need to create a character device node to
communicate with its applications. CUSE has full support for almost
all devfs functionality found in the kernel:
- kevents
- read
- write
- ioctl
- poll
- open
- close
- mmap
- private per file handle data

Requested by several people. Also see "multimedia/cuse4bsd-kmod" in
ports.