RFR(xxs): 8216982: Assertion poison page established too early

[Thomas Stüfe]

Hi all,

may I please have a review for the following fix:

cr:
http://cr.openjdk.java.net/~stuefe/webrevs/jdk-8216982-assertion-poison-page-established-too-early/webrev.00/webrev/
bug: https://bugs.openjdk.java.net/browse/JDK-8216982

In short, the assertion poison page is established during initialization
using os::reserve/commit_memory; however, the os:: subsystem is not yet
fully initialized at that point.

The patch moves the initialization after os::init_2(), it is now
established at the same point as the safepoint polling page. The
initialization can moved back safely - the only drawbacks would be asserts
happening earlier than this point not having register output in the error
file.

Thanks, Thomas