Add explicit keywords.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@48801 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Bitcode/Reader/BitcodeReader.h b/lib/Bitcode/Reader/BitcodeReader.h
index 9a140d9..86b00a5 100644
--- a/lib/Bitcode/Reader/BitcodeReader.h
+++ b/lib/Bitcode/Reader/BitcodeReader.h
@@ -117,7 +117,8 @@
   /// stream) and what linkage the original function had.
   DenseMap<Function*, std::pair<uint64_t, unsigned> > DeferredFunctionInfo;
 public:
-  BitcodeReader(MemoryBuffer *buffer) : Buffer(buffer), ErrorString(0) {
+  explicit BitcodeReader(MemoryBuffer *buffer)
+      : Buffer(buffer), ErrorString(0) {
     HasReversedFunctionsWithBodies = false;
   }
   ~BitcodeReader() {