RFR (XS): Fix Shenandoah argument checking on 32bit builds

[Roman Kennke]

This #ifdef _LP64 the part where we check for address space overflow
when using the optimized ObjArrayChunkedTask.

On JDK8u, this also replaces the use of the (2-arg) UNSUPPORTED_OPTION
with the 1-arg UNSUPPORTED_GC_OPTION (which was replaces with a 1-arg
UNSUPPORTED_OPTION in JDK9).

http://cr.openjdk.java.net/~rkennke/fixargchecks32/webrev.00/

Roman