RFR: (8031737) CHECK_NULL and CHECK_EXCEPTION macros cleanup (re-review)

[roger riggs]

Please re-review.

I missed a warning that the CHECK_NULL macros was being redefined.

Retaining the previous changes to java/util/jar/pack that removed the 
redefinition
addresses the issue.

The webrev now only has a few small changes to cleanup the name and use 
of CHECK macros.
The CHECK_NULL_* macros are more generally useful without the JNU_ prefix.
The JNU_CHECK_EXCEPTION* macros apply only when there is an jni environment.

Webrev:
     http://cr.openjdk.java.net/~rriggs/webrev-check-cleanup-8031737/

Thanks, Roger

[1] https://bugs.openjdk.java.net/browse/JDK-8031737