Unusual priority threads may no longer create new threads

The bug fix for 1250516 prevents any thread with "unusual" priority from creating
new threads. A thread with "unusual" priority is one outside the range
defined by MIN_PRIORITY..MAX_PRIORITY. Both the Solaris platform (the
clock handler) and Kona use such threads.

Because a thread picks up the priority from the parent, and the fix for 1250516
now value checks the priority (via setPriority), threads with unusual priority
cannot create new threads.

[a 29 May 96]

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Responding to the evaluation of 11 Jul 96,

There are two questions asked:

1. Why do we have threads with unusual priorities?
2. Why do these threads create other threads?

We have threads with unusual priorities for most system tasks, which must take
priority over application or applet tasks. Examples include the interrupt handling thread
and the clock handler thread.

Since these threads are quite prevalent, they could create other threads for a
variety of reasons, such as system initialization or restarting threads that
have died or been killed.

We could export the below-HPI level threads via sun.kona classes and
then provide an interface that provides equivalent functionality to
java.lang.Thread with the semantics of below-HPI threads instead of the
semantics of java.lang.Thread threads. This requires resolving some other issues,
such as what it means to execute Java code in the context of a non-java.lang.Thread
thread. This is something that could be investigated, but now doesn't seem
like the right time to do it.

[a 11 Jun 96]