Remove /^\s*#[#!]?\s*\$FreeBSD\$.*$\n/

This allows one to override the environment for processes created with
dtrace -c. By default, the environment is inherited.

This support was originally merged from illumos in r249367 but was lost
when the commit was later reverted and then brought back piecemeal.

Reported by:	Samuel Lepetit <slepetit@apple.com>
MFC after:	2 weeks

We can't link an executable using -m32 until the lib32 phase of a
buildworld, though the build works fine when executing make from
cddl/usr.sbin/dtrace/tests. Some other solution will need to be found.

The err.user64mode.ksh test expects it to run as a 32-bit process.

MFC after:	1 week

testing.

This test times-out on a quiet system because there is nobody triggers
syscall::open:entry or syscall::: probe while test execution.

Reviewed by:	gnn, markj (earlier version)
Differential Revision:	https://reviews.freebsd.org/D11671

after r298107

Summary of changes:

- Replace all instances of FILES/TESTS with ${PACKAGE}FILES. This ensures that
  namespacing is kept with FILES appropriately, and that this shouldn't need
  to be repeated if the namespace changes -- only the definition of PACKAGE
  needs to be changed
- Allow PACKAGE to be overridden by callers instead of forcing it to always be
  `tests`. In the event we get to the point where things can be split up
  enough in the base system, it would make more sense to group the tests
  with the blocks they're a part of, e.g. byacc with byacc-tests, etc
- Remove PACKAGE definitions where possible, i.e. where FILES wasn't used
  previously.
- Remove unnecessary TESTSPACKAGE definitions; this has been elided into
  bsd.tests.mk
- Remove unnecessary BINDIRs used previously with ${PACKAGE}FILES;
  ${PACKAGE}FILESDIR is now automatically defined in bsd.test.mk.
- Fix installation of files under data/ subdirectories in lib/libc/tests/hash
  and lib/libc/tests/net/getaddrinfo
- Remove unnecessary .include <bsd.own.mk>s (some opportunistic cleanup)

Document the proposed changes in share/examples/tests/tests/... via examples
so it's clear that ${PACKAGES}FILES is the suggested way forward in terms of
replacing FILES. share/mk/bsd.README didn't seem like the appropriate method
of communicating that info.

MFC after: never probably
X-MFC with: r298107
PR: 209114
Relnotes: yes
Tested with: buildworld, installworld, checkworld; buildworld, packageworld
Sponsored by: EMC / Isilon Storage Division

Sponsored by:	EMC / Isilon Storage Division

Discussed with:	ngie, markj
Sponsored by:	EMC / Isilon Storage Division

For each test category, we generate a script containing ATF test cases for
the tests under that category. Each test case simply runs dtest.pl (the
upstream test harness) with the corresponding test files. The exclude.sh
script is used to record info about tests which should be skipped or are
expected to fail; it is used to generate atf_skip and atf_expect_fail calls.
The genmakefiles.sh script can be used to regenerate the test makefiles when
new tests are brought it from upstream.

The test suite is currently not connected to the build as there is a small
number of lingering test issues which still need to be worked out. In the
meantime however, the test suite can be easily built and installed
manually from cddl/usr.sbin/dtrace/tests.

Reviewed by:	ngie
Sponsored by:	EMC / Isilon Storage Division