- eventlog.h: Add LIST_ENTRY to EVENTSOURCE structure to track handles.

- eventlog.h: Add LIST_ENTRY to EVENTSOURCE structure to track handles.
- ElfCreateEventLogHandle: Modify return type to PEVENTSOURCE and add BOOL parameter to determine whether handle is being created or opened as behavior differs between the two.
- Added ElfGetEventLogSourceEntryByHandle for looking up the handle.
- Implement EventLog api's ElfrOpenELW, ElfrRegisterEventSourceW, ElfrReadELW, ElfrReportEventW, ElfrOldestRecord, ElfrCloseEL and ElfrDeregisterEventSource.
- LogfWriteData: Remove unnecessary debugging.

svn path=/trunk/; revision=41202