Fix inappropriate use of anonymous namespaces in unittests.

The TEST_F macros actually declare *subclasses* of the test fixtures.
Even if they didn't we don't want them to declare external functions.
The entire unit test, including both the fixture class and the fixture
test cases should be wrapped in the anonymous namespace.

This issue was caught by the new '-Winternal-linkage-in-inline' warning.

llvm-svn: 158798