RFR 8216327 [lworld][c1] checkcast for value type should throw NullPointerException with null operand

[Ioi Lam]

https://bugs.openjdk.java.net/browse/JDK-8216327
http://cr.openjdk.java.net/~iklam/valhalla/8216327-c1-checkcast-null.v01/

Please review this small fix.

When we have something like this:

static Point test() {
     Object o = null;
     Point p = (Point)o;
     return p;
}

Deoptimize and let the interpreter generate the NPE.

Thanks
- Ioi