Hotspot current allows a user to map Java thread priorities (1-10) to OS native
priorities via the 10 JavaPriority<n>_To_OSPriority switches. We could add
another set of 10 switches, call them JavaPriority<n>_To_OSSchedulingClass,
to specify the scheduling class as well.

This CR

7082553: Interpret Thread.setPriority(Thread.MAX_PRIORITY) to mean FX60 on
         Solaris 10 and 11

went a little way down the path of being able to specify an alternative
scheduling class. In that CR, critical thread priority maps to the FX60
scheduling class/priority on Solaris. On other platforms, critical
priority maps to the same OS scheduling class and priority as MAX_PRIORITY.
This CR requests generalization of 7082553 to arbitrary scheduling classes
and non-solaris platforms.