Arm32 needs thread local handshakes support

[Robbin Ehn]

Hi all,

We want to remove the old global safepoint code, which is unused by most archs.
That code path is no longer tested or maintained by us.
- zero I sent out a patch for fixing it.
- x86 can just be switched over.
- Arm32 still relies on this, it must implement support for it.

Here is Andrew Haleys work for aarch64 as an inspiration for any takers:
https://bugs.openjdk.java.net/browse/JDK-8189596
http://hg.openjdk.java.net/jdk/hs/rev/efc459cf351e

Thanks, Robbin