JDK 9 RFR of JDK-8067289 (XS): Fix deprecation warnings in java.base module - CRC32C

[Staffan Friberg]

Hi,

Here is a small fix that avoids calling deprecated sun.misc.Unsafe 
methods, which allows the @SuppressWarnings to be removed.

Bug: https://bugs.openjdk.java.net/browse/JDK-8067289
Webrev: http://cr.openjdk.java.net/~sfriberg/JDK-8067289/webrev.00

Regards,
Staffan