When Tomcat starts up, both System.out and System.err are redirected to the
same PrintStream, an instance of o.a.tomcat.util.log.SystemLogHandler, which
itself wraps System.out
This happens quite early in o.a.c.startup.Catalina.load()
From then onwards no distinguish can be made between System.out.print()'s and
System.err.print()'s. The original 'System'-Error-Stream is lost.

Specifically when starting Tomcat within Eclipse (while developing/debugging a
Web-App), then the nice 'red' printed error-Stream instead of the 'blue' printed
stdout-stream is useless.