RFR(S): 8190432 [MVT] Value Types should have a default pre-allocated

[Frederic Parain]

Please review this small changeset to pre-allocate a default value:

Bug:
https://bugs.openjdk.java.net/browse/JDK-8190432

Webrev:
http://cr.openjdk.java.net/~fparain/8190432/webrev.00/index.html

The changeset injects a static field into each Java mirror of a
value type to keep a reference to the pre-allocated value.

All hotspot_valhalla tests pass.

Thank you,

Fred