More explicit keywords.

llvm-svn: 40673
diff --git a/llvm/lib/Transforms/Utils/LowerAllocations.cpp b/llvm/lib/Transforms/Utils/LowerAllocations.cpp
index 7ce2479..edc4c8a 100644
--- a/llvm/lib/Transforms/Utils/LowerAllocations.cpp
+++ b/llvm/lib/Transforms/Utils/LowerAllocations.cpp
@@ -37,7 +37,7 @@
     bool LowerMallocArgToInteger;
   public:
     static char ID; // Pass ID, replacement for typeid
-    LowerAllocations(bool LowerToInt = false)
+    explicit LowerAllocations(bool LowerToInt = false)
       : BasicBlockPass((intptr_t)&ID), MallocFunc(0), FreeFunc(0), 
         LowerMallocArgToInteger(LowerToInt) {}