RFR: JDK-8147388: Add diagnostic commands to attach JVMTI agent.

[Yasumasa Suenaga]

Hi all,

We can use Attach API to attach JVMTI agent to live process.
However, we have to write Java code for it.

If we can attach JVMTI agents through jcmd, it is very useful.
So I want to add two new diagnostic commands:

 * JVMTI.agent_load: Load JVMTI native agent.
 * JVMTI.javaagent_load: Load JVMTI java agent.

I maintain two JVMTI agents - HeapStats [1] and JLivePatcher [2].
[1] is native agent, [2] is java agent.
They provide a program for attaching to live process.

I guess that various JVMTI agents provide own attach mechanism like them.
I think that we should provide general way to attach.

I've uploaded webrev. Could you review it?
  http://cr.openjdk.java.net/~ysuenaga/JDK-8147388/webrev.00/

I'm jdk9 committer, however I cannot access JPRT.
So I need a sponsor.


Thanks,

Yasumasa


[1] http://icedtea.classpath.org/wiki/HeapStats
[2] https://github.com/YaSuenag/jlivepatcher  (in Japanese)