RFR(S): 8067231: Zero builds fails after JDK-6898462

[Severin Gehwolf]

Hi,

Could somebody please review and sponsor this small change? JDK-6898462
broke the Zero variant build by assuming that
Interpreter::remove_activation_entry() is defined for the C++
interpreter (which it is not). The proposed fix ifdef's it as it's done
elsewhere.

bug: https://bugs.openjdk.java.net/browse/JDK-8067231
webrev:
http://cr.openjdk.java.net/~sgehwolf/webrevs/JDK-8067231/webrev.01/

Thanks,
Severin