Summary
-------
JDK 5 introduced system property "sun.nio.ch.bugLevel" to deal with incompatible changes when moving from JDK 1.4 to JDK 5. This system property is now obsolete and can be removed.

Problem
-------

The main motivation for doing this is to eliminate a volatile String member which causes performance penalties when accessing the bugLevel() method used to test the property value.

Solution
--------

Remove the system property and the support for JDK 1.4 compatibility at the places where it is called.

Alternative would be to reimplement atBugLevel() method without volatile field.

Specification
-------------

The change implies that system property "sun.nio.ch.bugLevel" is ignored from now on. Before this change, one could set system property "sun.nio.ch.bugLevel=1.4" which would cause the following exceptional behavior to enable compatibility with JDK 1.4:<br>
a) The methods keys() or selectedKeys() of sun.nio.ch.SelectorImpl would not throw a ClosedSelectorException when the Selector is not open.<br>
b) The set of keys returned by keys() would not be an Immutable set and the set of keys returned by selectedKeys() would not be an ungrowable set.