Workaround for CPPUNIT_ASSERT_EQUALS tripping up on wstring.

Addresses tracker item 3671 using approach suggested by David Brooks in his comment.
Test whether compiler has codecvt.

Previous commit broke on older compilers.  Tracker item 3671.
CppUnit wstring fix wrap-up.

Some tests were missing the fix.
Also, moved the #include from .hpp to .cpp for previously fixed tests.
Tracker item 3671.
Merge pull request #6 from codecurve/CppUnit-wstring-workaround

Workaround for CPPUNIT_ASSERT_EQUALS tripping up on wstring.