Add explicit keywords.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@48801 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/CBackend/CBackend.cpp b/lib/Target/CBackend/CBackend.cpp
index 24ac8f9..b05c569 100644
--- a/lib/Target/CBackend/CBackend.cpp
+++ b/lib/Target/CBackend/CBackend.cpp
@@ -90,7 +90,7 @@
 
   public:
     static char ID;
-    CWriter(std::ostream &o) 
+    explicit CWriter(std::ostream &o)
       : FunctionPass((intptr_t)&ID), Out(o), IL(0), Mang(0), LI(0), 
         TheModule(0), TAsm(0), TD(0) {}