RFR: 8033289: clang: clean up unused function warning

[Henry Jen]

Hi,

Please review the fix that clean up unused function warning produced by 
clang 3.4.

http://cr.openjdk.java.net/~henryjen/jdk9/8033289/webrev/

One of those is used only in assert, so I wrapped it in #ifndef PRODUCT.

I had done a round of jprt along with other clang clean up, which passes 
all builds target.

Cheers,
Henry