RFR(XS): 8156088: Reintegrate 8153892: Handle unsafe access error directly in signal handler instead of going through a stub

[Mikael Vidstedt]

Please review the below changes - the reintegration of 8153892.

Bug: https://bugs.openjdk.java.net/browse/JDK-8156088
Webrev (hotspot): 
http://cr.openjdk.java.net/~mikael/webrevs/8156088/webrev.01/hotspot/webrev/

* Summary

The original change was broken. It turned out to be an ARMv7 specific 
problem, but since at the time the exact problem wasn't known the whole 
change was backed out by JDK-8156066. This change is a clean backout of 
the backout change.

Cheers,
Mikael