[jvm] Add some cleanup when intercepting exits.

The EvalServer adds a few minor headaches with memory usage, which we have to
take care off manually.  There's probably other ways still out there to reduce
memory usage, but this set at least finishes the Perl 6 spectest without hangs
or notable OutOfMemory exceptions.

src/vm/jvm/runtime/org/perl6/nqp/runtime/GlobalContext.java

@@ -307,6 +307,14 @@ public void exit(int status) {
 
         if (exitStatus < 0) exitStatus = status;
         shuttingDown = true;
+
+        for (Thread th : allThreads.keySet()) {
+            if (java.lang.Thread.currentThread() == th)
+                continue;
+            th.interrupt();
+        }
+        mainThread = null;
+        currentThreadCtxRef = null;
         throw new ThreadDeath();
     }
 

src/vm/jvm/runtime/org/perl6/nqp/runtime/LibraryLoader.java

@@ -125,7 +125,8 @@ public static Class<?> loadFile(String cf, boolean shared) throws Exception {
     }
 
     public static Class<?> loadNew(byte[] bytes, byte[] serial) {
-        return new IgnoreNameClassLoader(bytes, serial).loadClass();
+        IgnoreNameClassLoader incl = new IgnoreNameClassLoader(bytes, serial);
+        return incl.loadClass();
     }
 
     private static class IgnoreNameClassLoader extends ClassLoader {

src/vm/jvm/runtime/org/perl6/nqp/tools/EvalServer.java

@@ -197,6 +197,7 @@ private void eval() throws Exception {
                 if (entryRef == null)
                     throw new RuntimeException("This class is not an entry point");
                 Ops.invokeMain(gc.mainThread, entryRef, cuType.getName(), argv);
+                gc.exit(0);
             }
         }