RFR: JDK-8215648: remove equals and hashCode implementations from j.l.i.VarHandle

[Vicente Romero]

Please review fix for [1] at [2]. The fx is basically removing the 
implementation of methods VarHandle::equals and VarHandle::hashCode to 
make var handles consistent with method handles which don't override the 
default implementation for these methods,

Thanks,
Vicente

[1] https://bugs.openjdk.java.net/browse/JDK-8215648
[2] http://cr.openjdk.java.net/~vromero/8215648/webrev.00/