[C++11] More 'nullptr' conversion or in some cases just using a boolean check instead of comparing to nullptr.

llvm-svn: 205831
diff --git a/llvm/lib/IR/Use.cpp b/llvm/lib/IR/Use.cpp
index 60a0c56..e40f3e9 100644
--- a/llvm/lib/IR/Use.cpp
+++ b/llvm/lib/IR/Use.cpp
@@ -27,14 +27,14 @@
     Val = RHS.Val;
     Val->addUse(*this);
   } else {
-    Val = 0;
+    Val = nullptr;
   }
 
   if (OldVal) {
     RHS.Val = OldVal;
     RHS.Val->addUse(RHS);
   } else {
-    RHS.Val = 0;
+    RHS.Val = nullptr;
   }
 }