[turbofan] Build s/NULL/nullptr/g and CHECK(x != nullptr) to CHECK_NOT_NULL(x).

src/compiler/node.cc

Index: src/compiler/node.cc
diff --git a/src/compiler/node.cc b/src/compiler/node.cc
index bac783d66c38de77a6bb8428c9a915564ba42ff7..198c3530847f6124ca8eb39c57431a61875c6a96 100644
--- a/src/compiler/node.cc
+++ b/src/compiler/node.cc
@@ -60,8 +60,8 @@ Node* Node::New(Zone* zone, NodeId id, const Operator* op, int input_count,
   // Verify that none of the inputs are {nullptr}.
   for (int i = 0; i < input_count; i++) {
     if (inputs[i] == nullptr) {
-      V8_Fatal(__FILE__, __LINE__, "Node::New() Error: #%d:%s[%d] is NULL",
-            static_cast<int>(id), op->mnemonic(), i);
+      V8_Fatal(__FILE__, __LINE__, "Node::New() Error: #%d:%s[%d] is nullptr",
+               static_cast<int>(id), op->mnemonic(), i);
     }
   }
 #endif