Use nullptr instead of NULL for variadic sentinels

Windows defines NULL to 0, which when used as an argument to a variadic
function, is not a null pointer constant. As a result, Clang's
-Wsentinel fires on this code. Using '0' would be wrong on most 64-bit
platforms, but both MSVC and Clang make it work on Windows. Sidestep the
issue with nullptr.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221940 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/SjLjEHPrepare.cpp

@@ -99,7 +99,7 @@ bool SjLjEHPrepare::doInitialization(Module &M) {
                                       VoidPtrTy, // __personality
                                       VoidPtrTy, // __lsda
                                       ArrayType::get(VoidPtrTy, 5), // __jbuf
-                                      NULL);
+                                      nullptr);
   RegisterFn = M.getOrInsertFunction(
       "_Unwind_SjLj_Register", Type::getVoidTy(M.getContext()),
       PointerType::getUnqual(FunctionContextTy), (Type *)nullptr);