RFR: 8154041: JVMTI to Unified Logging

[Robbin Ehn]

Hi all,

Please review:

This moves jvmti trace output to the tag jvmti on trace level.

The jvmti trace argument e.g. "-XX:TraceJVMTI=ec+ieost,all+ieost" have a 
lot of functionality, e.g. can filter on func, in/out, etc, so it if 
left as is.

TraceJVMTI enables jvmti trace to stdout if no other -Xlog for jvmti tag 
is set.

Webrev: http://cr.openjdk.java.net/~rehn/8154041/
Bug: https://bugs.openjdk.java.net/browse/JDK-8154041

Thanks!

/Robbin