`SUBDIR.${MK_TESTS}+= tests` idiom.

This is a follow up to r321912.

directories to SUBDIR.${MK_TESTS} idiom

This is being done to pave the way for future work (and homogenity) in
^/projects/make-check-sandbox .

No functional change intended.

MFC after:	1 weeks

from the latter.

I'm starting with the easy cases.  The leftovers need to be looked at a
bit more closely.

Note that this change _does_ modify the code of the old tests.  This is
required in order to allow the code to locate the data files in the
source directory instead of the current directory, because Kyua
automatically changes the latter to a temporary directory.

Also note that at least one test is known to be broken here.  Actually,
the test is not really broken: it's marked as a TODO but unfortunately
Kyua's TAP parser currently does not understand that.  Will have to be
fixed separately.

Also add some missing $FreeBSD$ to keep svn happy.

help the GCC3 transition and CURRENT in general.

of the recent WARNS commits. The idea is:

1) FreeBSD id tags should follow vendor tags.
2) Vendor tags should not be compiled (though copyrights probably should).
3) There should be no blank line between including cdefs and __FBSDIF.