ShowRegistersOnAssert on by default

[Thomas Stüfe]

Hi all,

short note that we enabled ShowRegistersOnAssert
(https://bugs.openjdk.java.net/browse/JDK-8191101). We did add this
feature some months ago and ran our nightlies since then with it
enabled locally. Our compiler folks liked to have this on by default
so on it is.

I do not expect any problems, but should something go wrong you would
see a false segfault at the place where an assertion would normally
happen. Should you see this, please open a bug report and put it on my
name.

Note that for now, this only affects Linux (and not zero). Should
there be any interest and I have the time I will extend it to other
Posix platforms too.

Thanks Thomas