add jdk-test target, and fix failures

The intent of this target is to run our test suite against the installed jre.
This should help prevent our VM from diverging in implementation from the jdk.

The remainder of this commit fixes the problems that this exposes.

classpath/sun/misc/Unsafe.java

@@ -5,10 +5,10 @@ import java.lang.reflect.Field;
 public final class Unsafe {
   private void Unsafe() { }
 
-  private static final Unsafe Instance = new Unsafe();
+  private static final Unsafe theUnsafe = new Unsafe();
 
   public static Unsafe getUnsafe() {
-    return Instance;
+    return theUnsafe;
   }
 
   public native long allocateMemory(long bytes);