* NullEventLog.cs: Added dummy GetLogNames implementation.

* NullEventLog.cs: Added dummy GetLogNames implementation.
* EventLogImpl.cs: Moved GetEventLogs implementation to base class.
Added abstract GetLogNames method. Added ValidateCustomerLogName
method which should be called by eventlog providers when creating a
new log to ensure the significant part of the log name is unique, does
not match any of the special log names and does not match an exist event
source.
* Win32EventLog.cs: Validate customer log name when creating new log.
Moved GetEventLogs implementation to base class. Added GetLogNames
method.
* LocalFileEventLog.cs: Merged CreateLogStore into CreateEventSource.
Validate customer log name when creating new log. Moved GetEventLogs
implementation to base class. Added GetLogNames method.
* EventLogTest.cs: Added tests for log name validation in
CreateEventSource.

svn path=/trunk/mcs/; revision=64429