RFR: 8158150: LogConfiguration::describe output can get truncated

[Robbin Ehn]

Hi all,

The log configuration string for an output can be longer than O_BUFLEN.
The maximum size increase for each new tag set.

Webrev: http://cr.openjdk.java.net/~rehn/8158150/webrev/
Bug: https://bugs.openjdk.java.net/browse/JDK-8158150

Tested with internal vm tests and jcmd VM.log list

Thanks!

/Robbin