Return ENETDOWN when the parent interface is down.

MFC after:	1 week
cvsweb -> svnweb
Change callout use counter to use C11 atomics.

In order to get some coverage of C11 atomics in kernelspace, switch at
least one piece of code in kernelspace to use C11 atomics instead of
<machine/atomic.h>.

While there, slightly improve the code by adding an assertion to prevent
the use count from going negative.
Move _Atomic() into <sys/cdefs.h>.

That way _Atomic() is defined next to all the other C11 keywords for
which we provide compatibility for pre-C11 compilers. While there, fix
the definition to place "volatile" at the end. Otherwise pointer types
will become "volatile T *" instead of "T * volatile".
sys/dev/xen/blkfront/blkfront.c:
	In xbd_thaw(), fix inverted logic to verify the queue is frozen
	before attempting a thaw.

MFC after:	1 week
Re-sort ext2fs headers to make things easier to find.

In the ext2fs driver we have a mixture of headers:

- The ext2_ prefixed headers have strong influence from NetBSD
and are carry specific ext2/3/4 information.
- The unprefixed headers are inspired on UFS and carry implementation
specific information.

Do some small adjustments so that the information is easier to
find coming from either UFS or the NetBSD implementation.

MFC after:	3 days
Fix install from read-only obj dir when SHLIB_LDSCRIPT is used.

Reported by:    joeld
Tested by:      joeld
Fix OSVERSION variable within PBUILD_FLAGS.

Submitted by:	Garrett Cooper (in part)
Approved by:	kib (mentor)
MFC After:	1 week
X-MFC-With:	r251652
X-MFC-To:	stable/9 only
Add more obsolete files.
One more obsolete file.
Remove lines declaring "All rights reserved" or similar comments: they
are not true as the files are actually under the BSD-2 license

Approved by:	bushman
Fix the libc++ option.
This somehow got reverted when this was updated after the CVS removal.
Fix some missing symbols in the libsupc++ Version.map

MFC after:	1 week
Add myself as ports committer.

Approved by:	rm (mentor)
Added my another mentors: osa and eadler

Approved by:	rm (mentor)
Rename remaining DIAGNOSTIC to INVARIANTS.

MFC after:	3 days
Adjust i386 Xen PV support for updated Xen interface files.

sys/i386/include/xen/xenvar.h:
sys/i386/xen/xen_machdep.c:
sys/xen/interface/foreign/structs.py:
sys/xen/evtchn/evtchn.c:
	MAX_VIRT_CPUS => XEN_LEGACY_MAX_VCPUS

Submitted by:	Roger Pau Monné
Reviewed by:	gibbs
Remove vfs_mount(9), it have been died since 2004.

Noticed by:	git via alfred
MFC after:	2 weeks
 - Add a new UMA API: uma_zcache_create().  This makes a zone without any
   backing memory that is only a container for per-cpu caches of arbitrary
   pointer items.  These zones have no kegs.
 - Convert the regular keg based allocator to use the new import/release
   functions.
 - Move some stats to be atomics since they would require excessive zone
   locking/unlocking with the new import/release paradigm.  Make
   zone_free_item simpler now that callers can manage more stats.
 - Check for these cache-only zones in the public APIs and debugging
   code by checking zone_first_keg() against NULL.

Sponsored by:	EMC / Isilong Storage Division
- add my mentor -> mentee relation with koobs