Subzero: Fix an incorrect StringPool assert.

src/IceStringPool.h

Index: src/IceStringPool.h
diff --git a/src/IceStringPool.h b/src/IceStringPool.h
index e6b3d1117b10107fd276d048aad71f9580bf7d37..4b5f6dacbb1cdaf049490a2792c4d14caeffe9dd 100644
--- a/src/IceStringPool.h
+++ b/src/IceStringPool.h
@@ -118,7 +118,7 @@ public:
     if (!ThisHasString && !OtherHasString)

[Jim Stichnoth, 2016/04/07 12:20:50]

Here we test for both being false.

       return ID < Other.ID;
     // If exactly one has a string, then that one comes first.
-    assert(!OtherHasString);
+    assert(ThisHasString != OtherHasString);

[Jim Stichnoth, 2016/04/07 12:20:50]

This is just meant to validate that one is true and the other is false.

     return ThisHasString;
   }