test_syntax: fix test_main and mark so nosetests will ignore it

test_syntax: fix test_main and mark so nosetests will ignore it

* fix TestGentoolkitHelpers2 -> TestForSyntaxErrors
* use unittest.TestLoader and TextTestRunner instead of test.test_support

From the Python documentation [1]:

  The test package is meant for internal use by Python only. It is
  documented for the benefit of the core developers of Python. Any use
  of this package outside of Python's standard library is discouraged
  as code mentioned here can change or be removed without notice
  between releases of Python.

[1]: http://docs.python.org/2/library/test.html