Please make "RollFile" virtual so that we can enhance rolling strategies

I enhanced the RollingFileAppender so that you can roll to S3 (I call it RollingS3FileAppender). Right now, I have to duplicate all of the RollingFileAppender code because the RollFile method is not virtual.

Can this be worked into the next build?

NOTE: After trying to work with the RollingFileAppender, I decided that it would be "cleaner" to just write an S2Appender based on the AppenderSkeleton. Source code is available here:

http://s3appender.codeplex.com/