inaccurate System.currentTimeMillis() timer. Fortuately Sun introduced
System.nanoTime() in 1.5 which provides civilized timing information, so we can
use that instead of sun.misc.Perf which is unavailable in an applet sandbox. We
will need to go in and try to cope as best we can with currentTimeMillis() if
we want to support unsigned play in JDK 1.4 or earlier. We'll do that later.
git-svn-id: svn+ssh://src.earth.threerings.net/nenya/trunk@231 ed5b42cb-e716-0410-a449-f6a68f950b19