RFR: 8153723: Change the default logging output for errors and warnings from stderr to stdout

[Robbin Ehn]

Hi, please review!

This means that the default is -Xlog:all=warning:stdout
And has the pro that adding -Xlog:all=trace (implicit stdout) to your cmdline
will only print e.g. an error to stdout.
(now this will print one to stderr and one to stdout, on a tty this can be confusing)

Bug: https://bugs.openjdk.java.net/browse/JDK-8153723
Webrev: http://cr.openjdk.java.net/~rehn/8153723/webrev/

Passes hotspot_all.

Thanks!

/Robbin