test when an assert fails.

The following macro has been added:

	REQUIRE

An example of when these type of checks are useful:

    std::vector<int> v = foo();

    REQUIRE(CHECK_EQUAL(3, v.size())); // test stops here on a fail
                                       // so we don't segfault looking at
                                       // v[0] below.
    CHECK_EQUAL(1, v[0]);
    CHECK_EQUAL(2, v[1]);
    CHECK_EQUAL(3, v[2]);

Multiple checks are supported as follows:

    REQUIRE({
        CHECK_EQUAL(1, 2);
        CHECK(true);
    };

In the multiple check scenario, all the checks in the REQUIRE block will
be run. After which, if any failures were reported, the TEST case will
be stopped.

When UNITTEST_NO_EXCEPTIONS is defined, REQUIRE is a noop.

I changed the definition of the REQUIRE macro to use for loops and
some comma operator shenanigans to allow things like:

    REQUIRE
    {
      CHECK(...);
      CHECK_EQUAL(..., ...);
    }

or

    REQUIRE CHECK(...);

I updated the tests and they all passed on my machine. My only
concern is that some compilers might complain about the unreachable
code in the (throw UnitTest::AssertException(), true) expression.

(1) unreachable code in for loop shenanigans is eliminated.
(2) code after a failing REQUIRE check no longer executes. Used a
    decorating TestReporter to achive this.

Rather than re-using AssertException, it felt more correct to
create a new special-purpose exception.

Was able to remove ThrowingTestReporter::SetDecorated and
::GetDecorated by changing RequiredCheckTestReporter to accept
its TestResults by reference. This simple change removed
several if-checks and some functions.

Visual Studio 2015 complained about calling UT_THROW with zero arguments.
Visual Studio 6 complained about calling UT_CATCH with an empty second
argument. For these cases, I added UT_RETHROW(ExceptionName).

I also added a catch of RequiredCheckException to ExecuteTest to avoid
two error messages on each failed REQUIRE check.