Teach KTR_SCHED to handle changing thread names

[Julian Elischer]

On 12/23/11 12:20 PM, John Baldwin wrote:
> When I use the new schedgraph on 8, I find that it commonly calls almost all
> threads "sh" or "tcsh" because it only uses the name from the initial fork and
> never notices when a thread changes its name via exec.  This makes traces
> harder to follow.  The patch below adds a hook to clear the cached thread name
> to force it to be regenerated on the next trace when td_name changes.  This
> makes the traces more usable for me at least.
>
>
I have no problems with this..  hard to decipher debugging as as bad 
as no debugging.