SI-8601 Test that null.synchronized NPEs under -optimize

As part of my sweep through the side-effecting byte code instructions.

Author: retronym

test/files/run/t8601d.flags

@@ -0,0 +1 @@
+-optimize

test/files/run/t8601d.scala

@@ -0,0 +1,8 @@
+object Test {
+  def monitor(x: AnyRef): Unit = {x.synchronized(()); ()}
+  def check(x: => Any) = try { x; sys.error("failed to throw NPE") } catch { case _: NullPointerException => }
+
+  def main(args: Array[String]) {
+    check(monitor(null))
+  }
+}