[Java.Interop] Improve "Deleting JNI local reference" message.

Provide the current Thread.ManagedThreadId value in the
"Deleting JNI local reference...from wrong thread" message, along with
the current stack trace of the deletion.

Write the "Deleting JNI local reference" messages to
IJniHandleManager.WriteLocalReferenceLine(), so that the messages
don't "spam" stdout and are instead "in context" for LREF messages.

Author: jonpryor

src/Java.Interop/Java.Interop/JniEnvironment.cs

@@ -220,11 +220,21 @@ internal void LogCreateLocalRef (JniLocalReference value)
 
 		internal void DeleteLocalReference (JniLocalReference value, IntPtr handle)
 		{
-			if (lrefs == null || !lrefs.Contains (value)) {
-				Debug.WriteLine ("Deleting JNI local reference handle 0x{0} from wrong thread! Ignoring...", handle.ToString ("x"));
+			var c = current;
+			for ( ; c != null; c = c.previous) {
+				if (c.lrefs == null || !c.lrefs.Contains (value))
+					continue;
+				break;
+			}
+			if (c == null) {
+				JavaVM.JniHandleManager.WriteLocalReferenceLine (
+						"Deleting JNI local reference handle 0x{0} from wrong thread id={1}! Ignoring...",
+						handle.ToString ("x"), Thread.CurrentThread.ManagedThreadId);
+				JavaVM.JniHandleManager.WriteLocalReferenceLine ("{0}",
+						System.Activator.CreateInstance (Type.GetType ("System.Diagnostics.StackTrace")));
 				return;
 			}
-			lrefs.Remove (value);
+			c.lrefs.Remove (value);
 			JniEnvironment.Current.JavaVM.JniHandleManager.DeleteLocalReference (this, handle);
 		}