JKstat 0.60, handling kstat chain updates correctly

I've just updated JKstat, now up to version 0.60.

The key change this time, and the reason for a jump in version number (the previous was 0.53) is that I've changed the way that updates to the kstat chain are handled.

Now, libkstat has a kstat_chain_update() function, which you call to synchronize your idea of what kstats exist with the current view held by the kernel. And you can look at the return value to see if anything has changed.

This only works if you're running in a single thread, of course. If you have multiple threads, then it's possible that only one will detect a change. Even worse if you have a server with multiple clients. So, the only reliable way for any consumer to detect whether the chain has been updated is to retrieve the current kstat chain ID and compare it with the one it holds.

This has largely been hidden because I've usually used the KstatSet class to track updates, and it does the right thing. It checks the kstat ID and doesn't blindly trust the return code from kstat_chain_update(). (And it handles subsets of kstats and will only notify its consumers of any relevant changes.)

So what I've finally done is eliminate the notion of calling kstat_chain_update(), which should have been done long ago. The native code still calls this internally, to make sure it's correctly synchronized with the kernel, but all consumers need to track the kstat chain ID themselves.

This change actually helps client-server operation, as it means we only need one call to see if anything has changed rather than the two that were needed before.