context
It may be useful to pass a python object (e.g. class) to the ETW
processing callback. The ETW tracing API allows the user to fill out a
"Context" field with a pointer value that will be passed to the event
being sent, the rest is ctypes magic for wrapping the python object
into a native pointer value.
By default EnableTrace will listen with a "KeywordsAny" value of
0xffffffff. Some event log providers send events with keywords over
0x100000000, so we need a mecanism to filter on thoses keywords.
hakril