LowerBitSets: Move declarations to separate namespace.

Should fix modules build.

llvm-svn: 265176
diff --git a/llvm/lib/Transforms/IPO/LowerBitSets.cpp b/llvm/lib/Transforms/IPO/LowerBitSets.cpp
index 7b9879c..1798d83 100644
--- a/llvm/lib/Transforms/IPO/LowerBitSets.cpp
+++ b/llvm/lib/Transforms/IPO/LowerBitSets.cpp
@@ -33,6 +33,7 @@
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
 
 using namespace llvm;
+using namespace lowerbitsets;
 
 #define DEBUG_TYPE "lowerbitsets"