Remove regress getdents test, obsoleted by ATF tests

There are ATF tests using rumpkernel to verify getdents:
- tests/fs/hfs/t_pathconvert
- tests/fs/kernfs/t_basic
- tests/fs/vfs/t_union

branches: 1.8.36;
Remove the kernel and ipf tests that have been converted to atf and now
live in the tests subtree.

branches: 1.7.14;
Convert the regress/sys/fs/tmpfs tests to the atf

This change converts all the existing regression tests in
regress/sys/fs/tmpfs to the new framework provided by atf. As a side
effect, this also moves all the tests programs in regress/sys/fs/tmpfs to
tests/fs/tmpfs.

branches: 1.6.8;
Add simple lseek() test on a standard file. Standard it runs on the
/var/log/messages file wich is most likely not interesting but the
regression test can work on every specified filingsystem by passing a file
on that filingsystem to it as argument.

It tests:
- initial position
- seeking absolute position
- seeking end
- seeking negative relative position

more can be added later.

Descend into posix_fadvise/

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@).

test getdents(2). currently fail on nfs.

Add a regression test for mkdir(2) and rmdir(2).

Makefile for filesystem regression tests subdir.