Abolish all the silly indirection macros for initializing vnode ops tables.

These are things of the form #define foofs_op genfs_op, or #define
foofs_op genfs_eopnotsupp, or similar. They serve no purpose besides
obfuscation, and have gotten cutpasted all over everywhere.

branches: 1.13.72;
- Describe some locking.
- Add VOP argument comments, add some asserts.
- Update/fix/remove outdated/missleading comments.
- Clean up, de-indent, KNF, misc.

No functional changes intended.

branches: 1.12.2;
Add some support for unionfs (not built by default). It's still
missing at least opaque directory support, but until someone figures
out how that should work on ffs (see PR kern/kern/44383), there's
no point in trying to figure out how it should work here.

branches: 1.11.22;
Remove clause 3 and 4 from TNF licenses

branches: 1.10.6; 1.10.8; 1.10.10;
Remove VOP_LEASE. Discussed on tech-kern.

branches: 1.9.24; 1.9.30;
Add 2006 to the copyright notice; should have done this when touching the
files before.

Audit kqueue notifications. The reference behavior is taken from MFS and
is represented in the regression tests.

branches: 1.7.18; 1.7.22; 1.7.24;
- protect userland exported files against multiple inclusion.
- make sure that kernel only files don't compile in userland using #error
- XXX: some kernel only files still get installed.
- XXX: some files used in userland, don't get installed.

branches: 1.6.2;
merge yamt-vop branch. remove following VOPs.

VOP_BLKATOFF
VOP_VALLOC
VOP_BALLOC
VOP_REALLOCBLKS
VOP_VFREE
VOP_TRUNCATE
VOP_UPDATE

branches: 1.5.2;
Implement the tmpfs_advlock operation. Makes "user-level" file locking
work (aka lockf(3)).

Kill the tmpfs(9) manual page; it was just documenting internal details of
tmpfs' "API" and was already rotting.

Instead, merge all the relevant comments into the code. This includes
acknowledgements to Google's Summer of Code 2005 program (they were in the
AUTHORS section of tmpfs(9) before), so all the files need to be changed
to include this sentence alongside the title. (Note that this was not a
requirement of the program.)

- don't waste/leak kva.
- implement getpages/putpages. support mmap.
- eliminate meaningless memcpy.
- ubcify.

fix lock/unlock mismatch. XXX this is not a real fix.

Initial addition of tmpfs, an efficient memory file-system. This project
was developed as part of Google's Summer of Code 2005 program. This
change adds the kernel code, the mount_tmpfs utility, a regression test
suite and does all other related changes to integrate these.

The file-system is still *experimental*. Therefore, it is disabled by
default in all kernels. However, as typically done, a commented-out
entry is added in them to ease its setup.

Note that I haven't commited the required mountd(8) changes to be able
to export tmpfs file-systems because NFS support is still very unstable
and because, before enabling it, I'd like to do some other changes.

OK'ed by my project mentor, William Studenmund (wrstuden@).