Summary
-------

`ThreadInfo::from` should throw IAE when the given `CompositeData` does
not contain all the attributes specified for `ThreadInfo` of a specific version.

Problem
-------

`ThreadInfo::from` accepts `CompositeData` representing `ThreadInfo` of
the current and earlier release.   This method intends to validate the given
`CompositeData` and throw IAE if it does not represent a valid `ThreadInfo`.
For example, `lockedSynchronizers` and `lockedMonitors` must be present
if it represents JDK 6 or 9 `ThreadInfo`.   The spec needs clarification.
In addition while fixing this issue, `stackTrace` attribute represents 
`StackTraceElement` but the spec is missing `classLoaderName` attribute.

Solution
--------

Update the spec of `ThreadInfo::from` method to specify the release of each attribute 
was defined.  A valid `CompositeData` representing a `ThreadInfo` of version N 
must contain all the attributes defined <= N.  Same rule applies transitively to  
attributes whose type or component type is `CompositeType`.

Specification
-------------

See attached specdiff.