Better bytecode detection for Python > 3.0...

Not perfect though. More work is needed on the xdis side.

test/test_pyenvlib.py

@@ -80,6 +80,9 @@ for vers in TEST_VERSIONS:
     else:
         if vers == "native":
             short_vers = os.path.basename(sys.path[-1])
+            from xdis import PYTHON_VERSION
+            if PYTHON_VERSION > 3.0:
+                PYC = "*.cpython-%d.pyc" % int(PYTHON_VERSION * 10)
             test_options[vers] = (sys.path[-1], PYC, short_vers)
         else:
             short_vers = vers[:3]