default_set_sd rewrite (and updates test case) to fix the following:

* SetSecurityInfo should not reset owner and group to default if SECURITY_INFORMATION does not contain OWNER_SECURITY_INFORMATION or GROUP_SECURITY_INFORMATION
* The create functions for objects (create_event, create_mapping, create_mutex, create_semaphore) should set defaults if the security descriptor is NULL (it already did this properly if the security descriptor is empty). Other create functions will follow in a different commit.
* For certain objects: The impersonation token of the thread should also be used to determine the default owner, dacl, not just the primary token. (see http://msdn.microsoft.com/en-us/library/windows/desktop/ms686670%28v=vs.85%29.aspx )