Qualify use of "__builtin__.Exception" class.

It is possible that the module we're wrapping defines an Exception
class. This will confuse code that uses an unqualified "Exception"
class (e.g. "try: ... except Exception") since it now won't match
the Python builtin Exception. Fix this by explicitly using
the class from the __builtin__ module ("builtins" in Python 3).

Examples/test-suite/common.mk

@@ -218,6 +218,7 @@ CPP_TEST_CASES += \
 	evil_diamond \
 	evil_diamond_ns \
 	evil_diamond_prop \
+	exception_classname \
 	exception_order \
 	extend \
 	extend_constructor_destructor \