XMLLayout and HTMLLayout assume that the encoding of any associated writer is either UTF-8 or 
UTF-16.  If an encoding is not explicitly specified in the appender, the default platform encoding will be 
used which is highly unlikely to be UTF-8 or UTF-16 on Windows.  A mismatch in encoding will result in 
non-wellformed XML documents if a non-US-ASCII character is emitted in the log.

The proposed resolution is to add a new interface

interface EncodingSensitiveLayout {
    /*  @return encoding selected by layout  */ 
    String setEncoding(final String proposedEncoding);
}

to be implemented by XMLLayout and HTMLLayout.  In  the WriterAppender.activateOptions, if the 
layout supported EncodingSensitiveLayout, it would be passed the proposed encoding and would have a 
chance to either modify its behavior to be consistent with that encoding or to override the choice of 
encoding.