Update Python tests to not use flatstaticmethod access

Use Python class staticmethod syntax to access C++ static member functions,
such as Klass.memberfunction, instead of Klass_memberfunction.
Examples and test-suite changes in preparation for issue #2137.

Examples/test-suite/python/operator_overload_runme.py

@@ -1,7 +1,7 @@
 from operator_overload import *
 
 # first check all the operators are implemented correctly from pure C++ code
-Op_sanity_check()
+Op.sanity_check()
 
 pop = Op(6)/Op(3)