Add virtual destructor to please one of our compilers.

Change-Id: I931d130caa75ab90b677e14f1a2d0c438c43ed4f
diff --git a/compiler/optimizing/parallel_move_resolver.h b/compiler/optimizing/parallel_move_resolver.h
index f652db1..ff20cb0 100644
--- a/compiler/optimizing/parallel_move_resolver.h
+++ b/compiler/optimizing/parallel_move_resolver.h
@@ -33,6 +33,7 @@
 class ParallelMoveResolver : public ValueObject {
  public:
   explicit ParallelMoveResolver(ArenaAllocator* allocator) : moves_(allocator, 32) {}
+  virtual ~ParallelMoveResolver() {}
 
   // Resolve a set of parallel moves, emitting assembler instructions.
   void EmitNativeCode(HParallelMove* parallel_move);