Add explicit keywords.

llvm-svn: 48801
diff --git a/llvm/lib/ExecutionEngine/JIT/JIT.h b/llvm/lib/ExecutionEngine/JIT/JIT.h
index bf1e804..69e301b 100644
--- a/llvm/lib/ExecutionEngine/JIT/JIT.h
+++ b/llvm/lib/ExecutionEngine/JIT/JIT.h
@@ -37,7 +37,7 @@
   std::vector<const GlobalVariable*> PendingGlobals;
 
 public:
-  JITState(ModuleProvider *MP) : PM(MP) {}
+  explicit JITState(ModuleProvider *MP) : PM(MP) {}
 
   FunctionPassManager &getPM(const MutexGuard &L) {
     return PM;