inotify: make proper use of Python API to get object size.
In older python versions, it was ok to access an object's type by accessing its
ob_type "member". With python 2.6+, the proper way of accessing it is via
Py_TYPE(object). This patch implements the correct call for the inotify
extension. When under python < 2.6, this macro is defined in mercurial's
util.h.