RFR: 8143229: Replace the develop level with develop macros in Unified Logging

[Marcus Larsson]

Hi,

Please review the following patch to replace the previous 'develop' 
level with macros, in the unified logging framework.
The macros are essentially regular log calls inside a #ifndef PRODUCT. 
In the product they do nothing / return false.
This allows the regular log levels to be used for develop-only logging.

Webrev:
http://cr.openjdk.java.net/~mlarsson/8143229/webrev.00/

Issue:
https://bugs.openjdk.java.net/browse/JDK-8143229

Thanks,
Marcus