RFR: 8144146: Unified Logging tags cannot be reserved keywords

[Marcus Larsson]

Hi,

Please review the following patch to allow C++ reserved keywords to be 
used as UL tags. This allows usage of a 'class' tag, for example.

Tags are now automatically prefixed with underscores by the macros. This 
means they will still be referred to without underscores when used, but 
avoid keyword conflicts.

Webrev:
http://cr.openjdk.java.net/~mlarsson/8144146/webrev.00/

Issue:
https://bugs.openjdk.java.net/browse/JDK-8144146

Testing:
JPRT testset hotspot

Thanks,
Marcus