FX priority class from Solaris should be available to JVM

The FX class priorities should be available from within the JVM. Diffs attached
Solaris has an FX priority class that when certain threads are boosted to the highest priority (60) can gain significant performance advantages, especially on recent SPARC hardware. This patch allows the JVM to map from FX class to the internal JVM priorities. More work needs to be done to allow boosting individual threads to the highest priority.