use config.getoption instead of deprecated config.getvalue

and adapt a few tests to also run against pytest-2.6.0.dev

testing/conftest.py

@@ -7,7 +7,7 @@ pytest_plugins = "pytester"
 
 def pytest_addoption(parser):
     parser.addoption('--gx',
-       action="append", dest="gspecs", default=None,
+       action="append", dest="gspecs", 
        help=("add a global test environment, XSpec-syntax. "))
 
 def pytest_funcarg__specssh(request):