Subzero: Add -Wshadow to the build.

src/IceThreading.h

Index: src/IceThreading.h
diff --git a/src/IceThreading.h b/src/IceThreading.h
index f59f46e3bad590a55b23ba71732a95f6e2a864d9..7eb3c2a9f2553447114f72b039d9e07a1843934c 100644
--- a/src/IceThreading.h
+++ b/src/IceThreading.h
@@ -55,8 +55,9 @@ class BoundedProducerConsumerQueue {
   operator=(const BoundedProducerConsumerQueue &) = delete;
 
 public:
-  BoundedProducerConsumerQueue(bool Sequential, size_t MaxSize = MaxStaticSize)
-      : MaxSize(std::min(MaxSize, MaxStaticSize)), Sequential(Sequential) {}
+  BoundedProducerConsumerQueue(bool MySequential,
+                               size_t MyMaxSize = MaxStaticSize)
+      : MaxSize(std::min(MyMaxSize, MaxStaticSize)), Sequential(MySequential) {}
   void blockingPush(T *Item) {
     {
       std::unique_lock<GlobalLockType> L(Lock);