Switching to a safe version of NewChunk#bufX method due to crashes on Jenkins
Switching to a safe version of NewChunk#bufX method due to crashes on Jenkins

Jenkins builds showed the default implementation of NewChunk#bufX
can sometimes cause segfaults. We have seen similar behavior in AutoML
testing (rarely).

This was reported as a JDK bug, however, due to use of Unsafe API
the bug was rejected. We are providing an implementation of the bugX
method that doesn't rely on Unsafe and is turned on by default in this change.

h2oai/h2o-3,michalkurka/h2o-3,h2oai/h2o-3,michalkurka/h2o-3,h2oai/h2o-3,h2oai/h2o-3,michalkurka/h2o-3,h2oai/h2o-3,michalkurka/h2o-3,h2oai/h2o-3,michalkurka/h2o-3,michalkurka/h2o-3,h2oai/h2o-3,michalkurka/h2o-3,h2oai/h2o-3