2.0.13

Some minor updates:

• address deadlock with rolling file appender (https://issues.apache.org/jira/browse/LOG4NET-583)
• performance improvement for platforms not supporting WindowsIdentity (https://issues.apache.org/jira/browse/LOG4NET-652)
• allow using the netstandard2.0 libraries from within asp.net on net472 (#76)
• update to the log4j-alike output (#18)

This is essentially the same release as rc-1, with the artifacts updated so that unzipping them won't scatter files in the target.