Import GoogleTest 1.14.0

GoogleTest 1.14.0 now requires C++14 to build. Change
`googletest.test.inc.mk` to reflect this requirement.

Adjust the build integration logic to handle the new version of
GoogleTest (add/remove headers/sources as needed).

Tighten down warnings via `CXXFLAGS.clang` instead of ignoring all
warnings. Some new warnings snuck in after I did my last round of fix
submissions upstream.

Also address some overlinking added in the previous version import by
removing superfluous libraries.

===============================

Expect WhenDynamicCastToTest.AmbiguousCast to fail

This change reapplies the expected failure from 1.10.0.

Ref: https://github.com/google/googletest/issues/2172

MFC after: 2 weeks
Reviewed by: asomers, emaste
Differential Revision: https://reviews.freebsd.org/D41399

Merge commit '8ef491440fcaec96f899d73e08873426c78583a4' into googletest-v1.14.0-import

Import proof-of-concept for handling `GTEST_SKIP()` in `Environment::SetUp`

Per the upstream pull-request [1]:

```
gtest prior to this change would completely ignore `GTEST_SKIP()` if
called in `Environment::SetUp()`, instead of bailing out early, unlike
`Test::SetUp()`, which would cause the tests themselves to be skipped.
The only way (prior to this change) to skip the tests would be to
trigger a fatal error via `GTEST_FAIL()`.

Desirable behavior, in this case, when dealing with
`Environment::SetUp()` is to check for prerequisites on a system
(example, kernel supports a particular featureset, e.g., capsicum), and
skip the tests. The alternatives prior to this change would be
undesirable:

- Failing sends the wrong message to the test user, as the result of the
tests is indeterminate, not failed.
- Having to add per-test class abstractions that override `SetUp()` to
test for the capsicum feature set, then skip all of the tests in their
respective SetUp fixtures, would be a lot of human and computational
work; checking for the feature would need to be done for all of the
tests, instead of once for all of the tests.

For those reasons, making `Environment::SetUp()` handle `GTEST_SKIP()`,
by not executing the testcases, is the most desirable solution.

In order to properly diagnose what happened when running the tests if
they are skipped, print out the diagnostics in an ad hoc manner.

Update the documentation to note this change and integrate a new test,
gtest_skip_in_environment_setup_test, into the test suite.

This change addresses #2189.

Signed-off-by: Enji Cooper <yaneurabeya@gmail.com>
```

The goal with my merging in this change is to avoid requiring extensive
refactoring/retesting of test suites when ensuring prerequisites are met,
e.g., checking for a CAPABILITIES-enabled kernel before running capsicum-test
(see D19758 for more details).

The proof-of-concept is being imported before accepted by the upstream
project due to the fact that the upstream project is undergoing a potential
development freeze and the maintainers aren't responding to my PR.

1. https://github.com/google/googletest/pull/2203

Reported by: asomers (https://github.com/google/googletest/issues/2189)
Reviewed by: asomers
Approved by: emaste (mentor)
MFC after: 2 months
Differential Revision: https://reviews.freebsd.org/D19765

googletest: backport GTEST_SKIP to googletest 1.8.1

This commit backports revisions 00938b2b228f3b70d3d9e51f29a1505bdad43f1e and
59f90a338bce2376b540ee239cf4e269bf6d68ad from googletest's master branch to
our included version of googletest, which is based on 1.8.1. It adds the
GTEST_SKIP feature, which is very useful for a project like FreeBSD where
some tests depend on particular system configurations.

Obtained from: github.com/google/googletest
Sponsored by: The FreeBSD Foundation