avoid logViaPublicSLF4JLoggerAPI showing with log messages

[pruy]

Version 2.0.17
When using the fluent API (via atXXXX() methods on a Logger instance)
the resulting log message always shows "logViaPublicSLF4JLoggerAPI
as the calling method for %M message format token.
This is rather inconvenient when trying to get the method name with the log message.

I'd expect such functionality not showing an "internal" method.