Return value type fields in registers

[Roland Westrelin]

Hi Tobias,

> I've executed some quick testing on JPRT on top of Maurizio's latest patch:
> http://cr.openjdk.java.net/~mcimadamore/specialized_lforms_hs/
> http://cr.openjdk.java.net/~mcimadamore/specialized_lforms_jdk/

The only failure I see is:

#  Internal Error (/home/roland/valhalla/hotspot/src/share/vm/opto/parse3.cpp:554), pid=28067, tid=28104
#  guarantee(target_vcc_klass->derive_value_type() != NULL) failed: vbox: Target class must have a derived value type class linked

with runtime.valhalla.valuetypes.VboxUnbox that's reproducible with and
without my patch. With my patch and
-Dvalhalla.enableValueLambdaForms=true, everything else seems to work
fine.

Roland.