Fix Clang-tidy modernize-use-nullptr warnings in examples and include directories; other minor cleanups.

Patch by Eugene Zelenko!

Differential Revision: http://reviews.llvm.org/D13172

llvm-svn: 248811
diff --git a/llvm/examples/Kaleidoscope/Orc/initial/toy.cpp b/llvm/examples/Kaleidoscope/Orc/initial/toy.cpp
index 662c871..8dab73b 100644
--- a/llvm/examples/Kaleidoscope/Orc/initial/toy.cpp
+++ b/llvm/examples/Kaleidoscope/Orc/initial/toy.cpp
@@ -86,7 +86,7 @@
       LastChar = getchar();
     } while (isdigit(LastChar) || LastChar == '.');
 
-    NumVal = strtod(NumStr.c_str(), 0);
+    NumVal = strtod(NumStr.c_str(), nullptr);
     return tok_number;
   }
 
@@ -386,7 +386,6 @@
     return ErrorU<ForExprAST>("expected '=' after for");
   getNextToken();  // eat '='.
 
-
   auto Start = ParseExpression();
   if (!Start)
     return nullptr;
@@ -747,7 +746,7 @@
                                           const std::string &VarName) {
   IRBuilder<> TmpB(&TheFunction->getEntryBlock(),
                  TheFunction->getEntryBlock().begin());
-  return TmpB.CreateAlloca(Type::getDoubleTy(getGlobalContext()), 0,
+  return TmpB.CreateAlloca(Type::getDoubleTy(getGlobalContext()), nullptr,
                            VarName.c_str());
 }
 
@@ -759,7 +758,7 @@
   // Look this variable up in the function.
   Value *V = C.NamedValues[Name];
 
-  if (V == 0)
+  if (!V)
     return ErrorP<Value>("Unknown variable name '" + Name + "'");
 
   // Load the value.
@@ -959,7 +958,7 @@
 
   // Compute the end condition.
   Value *EndCond = End->IRGen(C);
-  if (EndCond == 0) return EndCond;
+  if (!EndCond) return nullptr;
 
   // Reload, increment, and restore the alloca.  This handles the case where
   // the body of the loop mutates the variable.
@@ -987,7 +986,6 @@
   else
     C.NamedValues.erase(VarName);
 
-
   // for expr always returns 0.0.
   return Constant::getNullValue(Type::getDoubleTy(getGlobalContext()));
 }